Some of the common cause of nightmares are:
Stress and Anxiety
Sickness with a fever
The death of a loved one
Effect of alcohol or excessive use of alcohol
Breathing disorders while asleep
And Sleeping disorders
Everyone's dreams happen during REM sleep, typically a person has 3-5 periods of REM sleep every night.
1 period of REM sleep can last from 5 minutes to 1 hour
20% of when a person is sleeping is REM sleep
e.g. if you slept 7-8 hours you will have an hour and a half of REM sleep.
Did you know if you wake up during the night you will be more likely to remember your dreams.