problems of the sleep

I have a disturb of the sleep (even if not too much often) and I want to know, if is it possible, of what could be.
when I sleep in wrong position (on the sofa, in the car,...)I have a strange phenomena:
to me it seems of being wide awake, to see what happens to me around, I want to be waked up but I can't move myself.
from outside,people look me that I make of the strange releases with my body,during the sleep.
In these moments I am badly, only after a few minuts I can to wake up myself.
what could be this disturbance?

thanks many for the kind aid.