I'd been experienced it before so I gather some research. Some expert says that this is because of over stress and tiredness before you sleep. Which causes of temporary paralyze. Some says who experienced this phenomenon, you should move your fingers of your feet so that you will be no longer to be paralyze that I haven't make because I didn't know that yet.
It depends on us whether we'll choose happiness over something else.
It was called as ADAPTATION, a mutation or genetic change, that helps an organism.