Periodic Limb Movement Disorder (PLMD)
This is a related condition involving involuntary, rhythmic limb movements, either while asleep or when awake. While most people who have Restless Legs Syndrome also have PLMD, only some people with PLMD also have RLS. Because of the discomfort the symptoms cause, RLS can make it difficult falling (and staying) asleep.  Alternative therapies, lifestyle changes, and even nutritional supplements have proven helpful for RLS and PLMD sufferers.

Narcolepsy
Narcolepsy is a disorder that causes a person to have difficulty staying awake. Narcolepsy can cause a person to suddenly fall asleep during the day. These “sleep attacks” occur even after getting enough sleep at night. The unusual sleep pattern that people with narcolepsy have can affect their schooling, work, and social life.
Symptoms:
Intermittent, uncontrollable episodes of falling asleep during the daytime
Excessive daytime sleepiness
Sudden, short-lived loss of muscle control during emotional situations
Hallucinations
Sleep paralysis
Nighttime wakefulness
Rapid entry into REM sleep

Night Terrors
Dreaming is a natural part of sleeping, everyone dreams, although some might not recall their dreams. However, sometimes dreams can turn really scary night Terrors. Night terrors occur during slow wave sleep.  They cause intense terror and partial arousal.  The sleeper may appear to be awake, sitting up, eyes open, but is actuality still asleep.  The person seldom remembers the episode or the dream the next
Symptoms:
Recurring abrupt arousals from sleep
Usually occur earlier in sleep than nightmares, often in the first third of the sleep period
Screaming
Intense fear
Rapid breathing and heartbeat
Sweating
No response to efforts to comfort the dreamer
No recall of the episode in the morning
No medical or mental cause for these episodes

REM behavior disorder
 This involves speaking (often profanely) and sometimes making violent movements during REM sleep, usually in response to a dream. People with rapid eye movement behavior disorder are sometimes aware of having dreamed vividly during these episodes when they wake up the next day.
Violent movements
Profane talking
Waving the arms, punching, and kicking, punching, kicking, leaping, or jumping from bed while still asleep

Dream-enacting behaviors

In today’s hectic world getting a good nights sleep has become a major issue. There are many reasons for this, the most obvious of course is stress but there are many other causes as well.
                   
Insomnia
Insomnia is a considerable lack of high-quality sleep. It can be short-term or chronic, and can  be caused by stress, change in time zones or sleep schedule, poor bedtime habits, or an underlying medical or psychiatric conditions.
Symptoms :
Difficulty falling asleep despite being tired
Requiring sleeping pills or alcohol to fall asleep
Awakening frequently during the night or lying awake in the middle of the night
Awakening too early in the morning despite not feeling refreshed
Daytime drowsiness, fatigue, and irritability

Sleep apnea
This is a common disorder that has the potential to become very serious, and even life-threatening. In sleep apnea, your breathing stops or gets very shallow while you are sleeping. Each pause in breathing typically lasts 10 to 20 seconds or more. These pauses can occur 20 to 30 times or more an hour.
Symptoms:
Frequent cessation of breathing (apnea) during sleep. Your sleep partner may notice repeated silences from your side of the bed.
Choking or gasping during sleep to get air into the lungs
Loud snoring
Sudden awakenings to restart breathing
Waking up in a sweat during the night
Feeling tired in the morning after a night’s sleep
Headaches, sore throat, or dry mouth in the mornings after waking up
Daytime sleepiness, including falling asleep at inappropriate times, such as during driving or at work

Restless legs syndrome (RLS)
This is a sensory disorder causing an almost overwhelming urge to move the legs. The urge to move the legs is usually due to uncomfortable, tingly, or creeping sensations that occur when at rest. Movement eases the feelings, but only for a while.RLS is not necessarily restricted to sleep time.
Symptoms:
Irritating sensation in legs
An overwhelming urge to move
Sensations that vary depending on position and time of day
Visible movements in toes or feet