I don't think I have anxiety, so this may be the wrong sub to post in, but I don't really know where else to ask. 
Last night I was settling down for bed, and as I was drifting off, it felt like my body was falling asleep at a much faster rate than my brain. It was  extremely uncomfortable as my whole body was shaking, and I felt my heart pounding. To be fair, I've had a similar experience regarding heart palpatations with melatonin, and that's why I got off of it. But this was something different. It was like my brain and my body refused to fall asleep in tandum, and it kept me up for 6 hours. I'm quite scared of going through that again. Does anyone have any advice?