Last night I woke up from a very light sleep, but it was like I was still dreaming. I had only been asleep for a half hour. I went to the bathroom and I noticed that My whole body was shaking.. Like vibrating, like the floor was moving beneath me. It was really scary, but I have experience from the past that if I obsess over a symptom, it just gets worse.
So I calmed down, and went back to sleep, and now everything is fine.