I have the same problem and these are real entities spirits that do this at night what ever you do do not be still and let them have their way. You must always fight your way out of it to wake up and then you can go back to sleep. They will test you time and again to see if they can take you. You can research this a little more on the net but from what I've read about it can be either a doorway to possession or what is known as a (Walk IN) soul exchange. If you allow that spirit to take over it can assume your whole identity if it wants so that the people you relate to will never know the difference but in reality it will have your body and you will be trapped on the astral plane. This is just my opinion and what I have learned from researching the subject however you are free to believe what ever you want concerning the matter.