Sleep paralysis. Happened to me a few times, started only the past 2 years. Smoking weed exacerbates it; also second hand smoke from cigarettes while you're sleeping. 3rd option is you could be under a voodoo / black magic attack so try to recall any bad enemies you might have made and imagine them being blocked away from you with a force field of your imaginations choosing.
Praying before I sleep for protection stopped it but some do still get through. The last one I had was from cigarette second hand smoke during my sleep; I had to get confrontational with my neighbor about it which I never usually do. Never came back after he stopped smoking in his room.