An internal clock in your body causes you to feel sleepier at night and more awake and alert during the day.

Disorders that interfere with sleep are known as parasomnias. 

RLS is a condition that makes people constantly want to move their legs, usually in response to an uncomfortable feeling.

Insomnia is a common sleep problem that can make it difficult to get asleep, difficult to stay asleep, or lead you to wake up too early and be unable to sleep again.

Breathing repeatedly stops and starts during sleep, which is known as sleep apnea.

The central disorders of hypersomnolence are characterized by severe daytime sleepiness, which is present despite normal quality and timing of nocturnal sleep