I started having this problem of "vibrations" seeming to radiate from my brain stem when falling asleep and waking up about 1 year ago. Doctors didn't offer much in terms of explanation or solutions. Suspecting that a prior head injury (hit my head on the bottom of a swimming pool) I went to a special type of chiropractor that focuses on the Atlas (top vertebrae C1) and the condition improved. Recently it has come back full force and like many here I have gone through countless lab testing, scans, evaluations, and found more that is normal than abnormal; which is comforting in some ways and frustrating in other ways. I have read this entire thread and my thoughts are that I'm dealing with some internal inflammation - perhaps due to a virus/long COVID effects as well as some low levels of Vitamin D and B12 and other nutrients so I am making adjustments to my diet and taking supplements. It's comforting to know that I'm not alone in this experience and I will follow up if I find a solution or ways to reduce it.