I've read through all the comments here, it's exactly what's happening to me. I'll wake up around 3am with cold sweats and a throbbing head, I see colors and lights rushing around in my vision, then eventually I have to run to the bathroom to vomit 2 or 3 times, and then I have a very uncomfortable time falling back to sleep. The weird thing is, I'll feel fine the day before it happens, and the next day I also have no symptoms, but a few days later it will happen again. I'm thinking it's some sort of neurological problem. Has anyone figured this out?