There are different types of sleep disorders that have different symptoms. Here are some of the different types:

Insomnia is the inability to fall asleep. It is a common sleep problem that most people experience at least occasionally. When it occurs, people feel tired much of the time and often worry a lot about not getting enough sleep. Consequently, insomnia often disrupts daily life. Some things that can cause insomnia are stress, diet, emotional difficulties and other underlying diseases.

Sleep apnea is interrupted breathing during sleep. It usually occurs because of a mechanical problem in the windpipe, but it also can indicate a neurological disorder involving nerve cells (neurons). As people age, muscle tone relaxes, which may cause the windpipe to collapse.

REM sleep behavior disorder causes disruptions in the brain during REM sleep. During REM (i.e., the dream phase of sleep), an area of the brainstem called the pons sends signals to the cerebral cortex, which is the area of the brain responsible for thinking and organizing information.

http://www.helpguide.org/life/sleep_disorders.htm

There are actually over 84 different kinds of sleep disorders. Some are more common than others. One sleep disorder is called hypersomnia. This is a condition where someone sleeps typically more hours than normal people-usually consistently over ten hours a day. These individuals can fall asleep at almost any time like at work or even while they are driving. This is one disorder that if someone with hypersomnia is driving and falls asleep and he might kill someone accidentally. This is deadly.

Sleep apnea is a more common kind of sleep disorder but it can be a life-threatening condition. Individuals that have sleep apnea stop breathing for ten to thirty seconds at a time while they are sleeping. These episodes can happen up to 400 times in one night. A person who has sleep apnea increases their chance of having a stroke or heart disease. People who have this disorder can fall asleep while driving because they do not get restful sleep.