I've been experiencing sleep paralysis for a couple of years, now and then, mostly when I just take a nap in the afternoon, which I do sometimes.

However, the last two nights I've been experiencing it at least 4 times.

I have a few questions about it:

When it starts, I hear a lot of loud sounds and noises, from inside my head, and it feels like everything is vibrating, is that normal, and what causes it?
The only things I can move is my mouth (very little) and my eyes. This is often really scary, and before I read anything about it I never even thought of trying to stay in that state.

Tonight though, after reading about that it can be a direct gateway to LDs, I decided that I would try to wait it out... and I set my alarm to 5 am, and woke up, I then focused on going into that state, and I did...
I tried the breathing technique, but it didnt work that well, and I woke up from the SP, the second time last night I heard sounds, like a xylophone, then saw a black shape next to my bed...
Is it my mind playing tricks on me?

thankful for answers

//M.