Why do I wake up with an erection in the morning?

shocked good looking young man in bed looking down at his penisNighttime and early morning erections are a normal part of male penile health. The technical term for this is “nocturnal penile tumescence.” The exact cause isn’t understood, but nighttime and morning erections usually occur during a part of sleep called REM sleep. They’re thought to be important to maintaining healthy blood flow to and function of the penis.