Well in fairness to the OP I suppose I should point out that I have never woken to SP, and have never entered it other than voluntarily (in failed WILD attempt) usually I do manage to reach paralysis a few times in serious attempts, it has been a while now too but. At least when entering slowly from the waking state, it didn't come on fast. I also didn't experience anything except the inability to move (except of course if I wiggled my finger tips and broke out nearly instantly), I also had a feeling of being slightly compressed but I only noticed the reverse when I seemed to decompress as I came out, as If weight lifted from me.

So it may well be that waking into sleep paralysis is a bit different, but it is hard to see how re-entering it could be so different. Just be sure to try to wiggle those tips and you should break out.

As to 3cats post, I am still awake so if I had the sense of a monster (or whatever) it would be more a hallucination in my opinion rather than a dream image, but hypnagogic or hypnopompic either way I have never experienced anything like that.