Hi there, I have been experiencing almost exactly what you described for the past few weeks (maybe 2 months) and I am not having any luck finding out anything about it on the internet, either. I have found some forum posts from people saying they can get similar things to this when going through periods of major stress or anxiety, but I do not feel that is the case in my situation. I get it even when I am totally relaxed, like if I fall asleep while getting an acupuncture treatment (relaxing!) or while nursing my 8 month old (also relaxing!). I mentioned it to my doctor a while back when it first started but she did not seem too concerned, though she did say I could get my heart tested because at the time I had trouble telling if it was heart palpatations or this sort of "internal tremor". I didn't follow up because at the time it didn't seem that bad/frequent but now it is to the point where it is becoming rather worrisome and very regular, and I think it even wakes my baby up when she is sleeping next to me. A few things I tracked down through my own research which you may want to read more about, mention to your doc or get tested for (I plan to bring this up again): nervous system disorders (like seizures), heart arrythmias, sleep apnea (where you stop breathing during sleep), or maybe anxiety. If you find out anything please do post, and I'll try to do the same! Best wishes for peaceful sleep!