I've had a few sleep paralysis as well. It mostly happens when you're trying to lucid dream ,staying up too late, tired etc. I have to admit It's pretty damn scary sometimes.

The mistake from what I've read so far is when you're on a paralysis state you should not force yourself to wake up or to move your body. When you experience sleep paralysis, immediately close your eyes for a few seconds and then you'll get back to sleep. Don't let your eyes open because you might see (most likely from your imagination/dream) some creepy ****.