Sleep Paralysis

I recently watched a documentary on YouTube discussing sleep paralysis. It's pretty creepy how so many people from different parts of the world tend to see the same things.

My grandmother told me about a time when she had it happen to her. She claimed that when she woke up, unable to move, that she saw an old woman crawling back and forth just outside her bedroom door. She was a treasure trove of scary stories. I miss her.

Anyway, I've never experienced sleep paralysis myself, but the morbid part of me is just curious enough to want to.

Have any of you ever had that happen to you? Did you see anything?