For many years, unlike most people, I can easily fall asleep.  It is very frustrating.  In college, I would pop high doses of No-Doze, with little to no affect.  Onset usually occurs afternoon and later, though can occur in the morning, if I am in an uninteresting long meeting.  My eyes and head grow so heavy, foggy, no matter how much I struggle against, I can not fight the urge to fall asleep.  I'll nod off for several minutes, up to 20, and then I wake up and I am fine.  I researched narcalepsy and I do not have most of the symptoms.  I researched melatonin for people who have difficulty falling asleep.  Is it possible that I might produce too much melatonin through out my circadian cycle to cause these bouts with sleepiness to occur during daylight hours?