During REM sleep, the body enters an involuntary state of paralysis, most likely to prevent it from acting out whatever is happening in the person’s dreams.
People who have experienced sleep paralysis when waking up from REM often report bizarre sensations.
Many people claim to feel some sort of presence in the room or outright seeing a terrifying presence – the so-called sleep paralysis demon.
Other times, people report out of body experiences where they were seeing themselves asleep.
Tamara Jones, a 25-year-old student in Toronto, recalled seeing a terrifying creature during a series of sleep paralysis episodes.
source: express.co.uk