Sleep paralysis is the inability to move during awakening or falling asleep.
The scary thing about this phenomenon is that you are awake but you can't move or speak and you see unreal things or beings. Also, symptoms can be heavy feeling in the chest or back or a feeling of flying and levitate.People who experienced it described hallucinations as demons, creepy creatures and dark clouds above them. Scientists still don't know why sleep paralysis happens.
While we are sleeping, our body is between REM which is rapid eye movement and NREM (non-rapid eye movement) sleep. One period of NREM and REM sleep happens in approximately 90 minutes. In NREM sleep, the body is relaxed and after NREM our sleep slowly shifts to REM. All of the muscles are "turned off" during REM sleep. If a human becomes aware before the REM cycle has finished then he can't do any move.
I haven't experienced sleep paralysis but I have two friends who actually did.
One of them told me how she once woke up and she saw a little black creature on her right side of the bed, but she couldn't move or anything else. She knew that she is in a sleep but she didn't know how to wake up. Later on that day she did online research about it and showed me a picture of creature assuring me that it was the same one she had seen during paralysis. It was completely incredible and scary. At first, it seemed weird to me, but she looked so upset while she was talking about it. It happened to her one more time and since then it has never happened again.
My another friend has sleeping problems too, but she can't sleep at all. She discovered that she had a sleep paralysis problem a year ago. Her case is more interesting because she believes that she must have experienced some kind of trauma when she was a little because any psychological problem can cause this phenomenon. I never knew that she was actually suffering from it. Even though she went to the psychiatrist, far and she decided to visit a priest. I am not sure did she went but she believes in paranormal activities. As she said, that is the only thing that could maybe help her.
I have sleeping problems very often, the first one is on nights of a full moon. Also, sometimes I can't sleep because I have increased energy that needs to get out. So I often ride my exercise bicycle in the middle of a night. You can call me crazy, but I would like to experience sleep paralysis!
@exanime15 