I was just lying in bed with my head on the pillow slipping into sleep, when suddenly I felt like I was hit on the top of the head with something like flat side of a shovel. My body tensed up and my head jolted as though it was hit. I was in a state of confusion and shock for a few seconds. Once I realized what happened, I thought it was interesting, but didn't really try to find anything out about the occurrence. Now I am starting to wonder, is there a technical term for that sort of occurrence, and how often does something like that happen on average?
I would really like to hear about other peoples experiences with this kind of thing as well.