A few hours of restful sleep each night gives you a great sense of satisfaction. And what’s behind that sense of satisfaction? Sleep stimulates the mind. Sleep renews the body. You just feel better. For some people, a night of restful sleep is very rare. They toss. They turn. They wake up bleary-eyed the next morning, desperate for caffeine. Is this you? Take a look at these 9 science-backed reasons that lead to a restless night.