I wasn't going to comment but decided against it since this's my frequent condition. I actually get this a lot, and like you said, sometime I have this the whole night long. Wake up with this, then really wake up, fall asleep again because I was too tired, and get this again. All night long.
In my country, they call this 'bóng đè' or 'ma đè', basically means 'a shadow lying over you' or 'a ghost lying over you'. I also happen to have something with my 'spiritual energy' that actually welcome ghosts.
I've been living with sleep paralysis for four years. So I feel your fear, hey.