Once in a while, when I fall asleep at night, I'll suddenly jolt awake like I've had an electric shock go through me (adrenaline perhaps?). My heart will be racing and I'll be sweating. It goes away after a few minutes, then I fall asleep again and it happens again. I have nights where I'll wake up 3 or 4 times like this and other nights where it never happens. I usually have to take a xanax to stay asleep on nights like that. Has anyone else had this? I'm not on meds, so that can't be it.