"Where knowledge ends, superstitions begin.." ~Anonymous

Have you ever woken up heavily frightened after battling for a couple of minutes to even wake in the first place? Well, what you experienced is a natural phenomenon called sleep paralysis. It usually occurs alongside hallucinations that one is being attacked by an unseen force. Though very disturbing, it is not a serious condition and is just a case of one system overshooting the other.
During deep sleep, muscle tone throughout the body is exceedingly depressed but the brain is highly active as it were during wakefulness (this is why people get dreams - collections of your brain activity/thoughts during sleep. The brain is wonderful and some of its thoughts could be so powerful that you'd swear it was real. There are times we have dreams of ourselves urinating in the toilet, these dreams are so real that we believe we're in the toilet, only to wake up swimming in a pool of your own urine on the bed and you curse yourself thinking you were grown past all of these)

Ok let's get back...

Wakefulness also progresses in stages (from a sub-conscious state of wakefulness to a conscious state of wakefulness). During the subconscious state, the brain is very active but muscles throughout the body are paralysed as in deep sleep - this is sleep paralysis. During sleep paralysis, a person believes he is making attempts to get up meanwhile in actual fact he is just as still as during normal sleep. His brain is sending the normal motor signals to his muscles but not getting the appropriate response just yet. Sometimes people tend to fall back into another paralysis after having "woken up" from the first one, meanwhile in actual fact, the person never woke up at all. This continues for a while before everything synchronizes up and brain - muscle coordination is achieved. By now fear must have set in with faster heart beats, since the brain is not so used to these rare scenarios of muscles not acting out motor signals sent to it - this is as good as being dead.
Again all of these is normal. You are not being pressed, your muscles are just depressed.

Getting as much sleep as possible could help with the episodes - There seems to be some evidence that people who are sleep deprived enter deep sleep very quickly, which means they're still awake as their body gets paralyzed.

Seek care. Because sleep paralysis might be linked to other sleep anomalies, including deep sleep disruptions and narcolepsy, it's important to see a sleep specialist if your paralysis occurs often. And if you're dealing with high levels of stress or anxiety, consult a mental health professional.

My chief

Nice post