Horrible vibrating feeling ("body buzzing"/internal tremor)

The only symptom of MG is muscle weakness that gets worse after use. The feeling you describe could be related, but not an actual symptom. I had plenty of problems peripheral to MG that were troublesome to me but weren't considered part of the MG. Like tremors, nerve entrapment in my wrists and ankles, tingling in my feet, stiff muscles, and general fatigue.

It is not a diagnostic symptom for MG, but it could be that your body has this sensation when it gets weak. I hope you get this figured out soon. It sounds miserable.

I got an AChR antibody test ordered by my PCP before I even saw a neurologist. This is the most common type of antibody (85+% of cases) and just a simple blood test, so it's often the first test for MG.

Tests for MG are very specific and are only done when a provider suspects MG. You're not going to stumble upon a positive while doing "general testing", so make sure your neurologist knows you want to be tested specifically for MG. Even neurologists can be unfamiliar with MG. If possible, you'll want to see neuromuscular specialist.

Look into vitamin B -12 and also magnesium.

I’d see a movement disorder specialist too, I needed a referral from a neurologist first

I also experience this internal vibration sensation you are talking about but I attribute it to my POTS (Postural Orthostatic Tachycardia Syndrome). POTS is associated with many autoimmune diseases and is not uncommon, it could be worth looking into.

Sounds like serotonin syndrome. If you do have this, you need to see a doctor very soon, as in days.

I was getting buzzing, like nerve pain without pain before I was diagnosed. This disappeared after taking medication. Not sure if this is what you’re experiencing.

I get that feeling when my potassium is low. It reminds me of those old electric football games my brothers used to play with (I’m old - were talking the 1960’s). You lined your plastic football men up on this metal box that looks like a football field, then plug the darned thing in and the little men would jitter around the field. My dad and brothers loved that thing. But when my potassium drops, my body feels like those jittery little football men!

Are you on Prednisone? Through the process of elimination over years I finally figured out that feeling like an electrical current was running through my body was caused by Prednisone.

I get a strange buzzing/vibrating feeling, hard to describe as it is different from tremors, tingling, or numbness. Most often (daily) it’s a mild buzzing in arm/legs below knees/elbows during periods where I get excessive daytime sleepiness/fatigue or feel faint or woozy. Occasionally there are days I feel like my whole body is vibrating. I’m not sure if it is MG as these are not MG symptoms as far as the doctors are concerned. Though on a few extreme days the vibrating progressed to clear shaking and muscle weakness so I theorize maybe the buzzing is the disorder mucking with muscles before it reaches overt muscle weakness.

I tested positive for ACHr antibodies and am awaiting neurology appointment for official diagnosis/treatment.