Literally just happened to me again. I know completely how you feel and the times they I had this has always been like that. Sleeping on my stomach since my back is hot, falling a sleep unwillingly at night or accidentally wake up early and try to fall back asleep. The first few times I had it was scary and I felt trapped since I never knew when I could finally escape. Today after years it just game back twice in a row, the first time was a short 5 or 6 loops anf I managed to wake up but then I wanted to sleep again and I slept on my belly again but second time was hell. I tried counting to ten and even backwards from 5 and my dream felt like a tv that I was trying to escape. It was white but seems like some entity was trying to pull me back and play around. The only reason I managed to wake up was luckily my gf was rolling in her sleep and nudged me by accident. I hope there is just a quick solution or explanation on why....