Hiawawa, you were on the verge of having an out-of-body experience(OBE). I used to have them all the time, too. Yes, the sensation of "being held down" or not able to move is terrifying. I remember trying to scream, but being voiceless...
This happened to me in my early 20s...I was finally over to release my fear and enjoy the experience although I never traveled far...
And then, of course, since I was no longer afraid, they ceased. Or maybe that was the point at which my pineal gland became totally saturated with fluoride!
There were no "evil spirits" at work, not that I saw or felt. The fear was self-generated.