I've posted here previously but have been quiet recently. Internal vibrations have been linked to COVID (there are scientific articles on line from Yale and a few other places describing this), Vit D deficiency, cortisol and very few other things. All of which can be checked. They are real, as long as we as a group are not confusing them with essential tremor or some other defined neurological condition. I've seen some posts here (and have heard similar from some doctors) from folks that have abruptly stopped meds and then have internal vibrations or have painful conditions/other comorbidities. Some of us (you and I) have no health issues or potential triggers beyond 'coming out of sleep.' I've had every work up that exists it seems like; all to come back as normal or with minor abnormalities that RHUEMs, NEUROs, NEURO-SURG, SLEEP NEUROs, ENDOs and others can not confidently link to internal vibrations upon waking. There is a lack of data in this field and folks at the Mayo Clinic believe that too. I believe as you do that this is neurological or muscular sleep/wake 'glitch' in the system. I've been assured over and over that there is no evidence this is chipping away at my health so I've stopped worrying about it (for now). You and I are aligned.

@edornton my experience is almost identical to yours, except my shakes/vibrations tend to be more focused in my forearms and hands. I also noticed if I’m laying on my back upon wake up, I can feel it across my back sometimes up my neck to the back of the head. Only on occasion have I felt it elsewhere, but on the days that it’s barely there, I will just feel it in my fingertips. Also same, nothing alarming with my primary care doctor, every aspect of bloodwork in normal range aside from B12 (but I’ve always struggled with that deficiency) and neurologist basically said he has no other answers after ruling out any autoimmune, and apparently didn’t feel it warranted a CT scan or anything. I’ve had it happening for 19 months straight now and have a referral for another neurologist that I might follow up with. Taking magnesium glycinate before bed seems to help and staying hydrated and being aware of my sugar intake near bedtime sometimes seems to make a difference, but not always. I agree that it has to be something abnormal within the sleep process (also did a sleep study and determined I have mild apnea, but no proven relation to the vibrations), because I have zero symptoms of anything else for every other waking hour of the day.