Narcolepsy is characterized by episodes of frequent, uncontrollable daytime sleeping, usually preceded by drowsiness. The episodes usually occur after meals, but sudden onset of sleep may occur while working or driving a vehicle, having a conversation, or being in any sedentary or nonstimulating situation.
There is a brief period of sleep, and the person awakens feeling refreshed. However, he or she may again become uncontrollably sleepy a short time later.