i been having these feeling all the time and always wounder what it is.

I went to sleep and stay absolutely still without even moving any single my muscle. Then sometime later i begin to feel my blood going through my body (Normal) now here's the weird part - my mind starts to spin in circle again and again then it stop, after about 30 seconds i raise my arm and it's all numb.
Someone please tell me what it is.

PS: maybe it's that thing in the other post about "how to trick your body to sleep" or maybe not. Or maybe it's me using CHI...maybe