Internal Tremors and Vibrations in Long COVID and Dysautonomia

If you feel a shaking, buzzing, or vibrating sensation inside your body, in your chest, your legs, your core, or all over, and yet nothing actually trembles when you look, you are describing internal tremors, and they are one of the most unsettling symptoms of long COVID and dysautonomia. They are also one of the most misunderstood, because the classic response (“but I can’t see anything”) leaves a lot of people feeling dismissed. Internal tremors are real, they are common after a viral illness, and in most cases there is a clean physiological reason for them.

This article explains what internal tremors and vibrations are, why a dysregulated autonomic nervous system produces them, when they are worth getting checked, and how to read your own pattern without letting it frighten you. These are educational field notes, not medical advice. Tremor has more than one cause, so nothing here diagnoses anything, and a tremor that is new, one-sided, or visibly getting worse belongs in front of a clinician.

What are internal tremors?

An internal tremor is a felt vibration with little or no visible movement. People describe it in strikingly consistent ways: a phone-on-silent buzz deep in the chest, a car-idling hum in the torso, legs that feel like they are shaking though they are still, a fine trembling that seems to come from the bones rather than the surface. It can be constant or come in waves, it can sit in one region or move around, and it very often has a daily rhythm, worst on waking or when tired and quieter later in the day.

The key feature is the mismatch: the sensation is strong, but an observer sees nothing, and even you, watching your own hand, may see nothing. That mismatch is exactly why internal tremors get brushed off, and it is also the clue to what is happening. You are feeling a tremor that is real but too small to see.

Why dysautonomia and long COVID cause them

The mechanism behind most internal tremors in this population has a name: enhanced physiological tremor.

Start with the baseline. Every healthy person has a constant, faint tremor in their muscles, oscillating at roughly 8 to 12 cycles per second. It comes from the rhythm of your heartbeat pushing through tissue, the firing patterns of motor neurons, and the mechanical properties of muscle. Normally it is far too small to see or feel. It is just there, in the background, all the time.

Now add adrenaline. Adrenaline (and its cousin noradrenaline) acts on beta-adrenergic receptors in your muscles, and one of the effects is to increase the amplitude of that background tremor. This is not unique to illness. It is why your hands shake after a fright, after too much coffee, or when you are on stage. The tremor was always there; stress hormones made it big enough to notice. When it gets amplified but stays fast and fine, you often feel it as an internal buzz rather than see it as a shake.

Here is where long COVID and dysautonomia come in. A common legacy of a post-viral illness is an autonomic nervous system stuck with the sympathetic “fight or flight” branch running high, generating adrenaline surges far more readily than it should. That is the same dysregulation behind adrenaline dumps in POTS, morning tachycardia, and much of the racing-heart, wired-but-tired quality of these conditions. Put a hair-trigger adrenaline system on top of a normal physiological tremor, and you get a tremor that is amplified much of the time, felt from the inside, and worst at the moments adrenaline peaks.

Several things stack on top of this in long COVID and dysautonomia:

• Small fiber neuropathy. Damage to the small autonomic and sensory nerves is well documented after COVID and in POTS, and can distort how the body senses and steadies itself (more in small fiber neuropathy in POTS and long COVID).
• Poor and fragmented sleep. Under-recovery raises sympathetic tone the next day, and morning is already the highest-adrenaline part of the cycle.
• Low blood volume. A core problem in POTS; the body compensates for low volume with more sympathetic drive, which means more circulating adrenaline.
• Deconditioning and blood-sugar swings. Both push the stress system to work harder to keep you upright and fueled.
• Anxiety, when it is present. A sensitized nervous system and a frightening symptom feed each other, and anxiety raises adrenaline, which raises tremor. This is a real amplifier, not a dismissal of a physical symptom.

The through-line is simple: internal tremors in this setting are usually a symptom of an over-active stress response, not of a damaged brain. That distinction matters, because it means the levers that calm the stress response tend to calm the tremor.

When do internal tremors show up?

Because the driver is adrenaline, internal tremors cluster at the body’s high-adrenaline moments. Recognizing your own timing is the first step to reading them calmly.

The most commonly reported triggers and timings:

• On waking and in the early morning, when cortisol and adrenaline naturally surge to get you up. Many people describe waking already buzzing.
• On an empty stomach or with a blood-sugar dip. A falling glucose level triggers an adrenaline response to correct it, which amplifies tremor. This overlaps with reactive hypoglycemia in POTS.
• After a poor night’s sleep, which leaves sympathetic tone elevated the next day.
• During or after a crash / post-exertional malaise, when the body is under strain.
• With caffeine, nicotine, and other stimulants, which are direct adrenergic pushes on top of an already sensitive system.
• When standing or upright, especially in POTS, as the body ramps up sympathetic drive to defend blood pressure.

Internal tremor versus visible tremor

It helps to be precise about what you are feeling, because the words point at different mechanisms and different next steps.

A fine, fast, symmetrical tremor that flares with adrenaline and eases with rest fits the enhanced-physiological picture. A coarse, slow tremor, a tremor present at rest, a one-sided tremor, or one that is steadily getting worse is a different pattern and should be assessed properly.

What else can cause tremor, and what to rule out

Internal tremors are usually autonomic in this population, but “usually” is not “always,” and the sensible move is to make sure the treatable and the important causes have been considered. None of this is a reason to panic; it is a reason to get a basic workup so you can stop wondering.

Common and worth checking:

• Thyroid overactivity (hyperthyroidism). A classic cause of fine tremor, and it also raises heart rate and heat intolerance. A simple blood test settles it (see thyroid, HRV, and POTS).
• Low blood sugar. Hypoglycemia triggers adrenaline and tremor; steady meals and, if needed, testing can clarify it.
• Vitamin B12 and other deficiencies. Low B12 can cause neurological symptoms including tremor and buzzing sensations, and is easily tested and corrected.
• Medications and substances. Stimulants, some asthma inhalers (beta-agonists), certain antidepressants, thyroid replacement, and caffeine all increase tremor; alcohol withdrawal is a notable cause.
• Anxiety and panic. Real contributors through adrenaline, and they can coexist with a physical cause rather than replace it. See is it POTS or anxiety.
• Neurological conditions. Essential tremor, Parkinson’s disease, and multiple sclerosis can cause tremor, which is exactly why a new, progressive, one-sided, or rest tremor deserves a clinician’s eye rather than an internet guess.

How to ease internal tremors

Because the common driver is an over-active stress response, the reliable levers all lower sympathetic load. None of these is a cure, and results are individual, but together they move the pattern for most people.

• Pace to avoid crashes. Post-exertional crashes are high-adrenaline states. Staying inside your energy envelope is one of the most effective things you can do for the whole symptom cluster, tremor included.
• Protect sleep. Under-recovery raises next-day sympathetic tone. Consistent sleep and wake times, a dark cool room, and a wind-down routine all help (sleep and autonomic recovery).
• Eat on a steady schedule. Regular meals with some protein blunt the blood-sugar dips that trigger adrenaline. If mornings are the worst, a small snack soon after waking often takes the edge off.
• Reduce stimulants. Caffeine and nicotine are direct adrenergic pushes. Cutting back, especially in the morning and afternoon, frequently lowers the baseline buzz.
• Support blood volume, if it applies to you. In POTS, fluids and salt reduce the sympathetic compensation for low volume; work out your own targets with a clinician, especially with any blood-pressure or kidney concerns (science of salt and fluids).
• Down-regulate the nervous system directly. Slow, extended-exhale breathing shifts you toward parasympathetic tone in minutes and is a genuinely useful tool during a flare (resonant breathing and HRV biofeedback).
• Treat what is treatable. If thyroid disease, a B12 deficiency, a medication effect, or an anxiety disorder is contributing, addressing it directly can resolve a large share of the tremor.
• Ask about beta-blockers. Because enhanced physiological tremor is a beta-adrenergic effect, beta-blockers can blunt it directly, and are already used for related autonomic symptoms. This is a physician’s decision, not a DIY one (beta-blockers and HRV).

Reading your own pattern without spiraling

The single most useful thing you can do with a frightening symptom is turn it into information. Internal tremors feel random and threatening; on a timeline they usually turn out to be patterned and tied to adrenaline, and that shift, from “something is wrong with me” to “this is my stress response reacting to X,” is itself calming.

• Log when it happens and what it feels like. Time of day, location in the body, constant or wave-like, and intensity. A simple symptom and trigger journal is enough to surface the timing.
• Note the context. Sleep the night before, whether you had eaten, caffeine, standing, stress, and where you are in a crash cycle. The triggers above become obvious once a few days are logged.
• Watch it beside your autonomic numbers. Internal tremors rarely travel alone. A buzzing morning is often also a high-resting-heart-rate, low-HRV morning, because they share one driver. Seeing the tremor land on the same days your other signals show high sympathetic tone confirms the mechanism and takes some of the fear out of it.

The bottom line

Internal tremors and vibrations are a real, common, and usually benign feature of long COVID, POTS, and dysautonomia. In most cases they are enhanced physiological tremor: the faint tremor everyone’s muscles produce, turned up by a sympathetic nervous system running high and by adrenaline that surges too easily. That is why they spike on waking, on an empty stomach, after poor sleep, and during a crash, and why the same steps that calm the stress response, pacing, sleep, steady meals, fewer stimulants, blood-volume support, and slow breathing, tend to calm the tremor. They are not, on their own, a sign of damage. But tremor has other causes worth ruling out, so get a basic workup, watch for the red-flag features, track your own pattern beside your other autonomic signs, and bring the specifics to a clinician who can interpret them.