After mild sleep deprivation OR caffeine/stimulant withdrawal, I crash hard. I fall asleep wherever I am and can't really fight the urge. After waking from my nap, I feel unbelievable tired, weak and almost paralyzed. For the next 1-4 hours I feel as if my brain is swollen. So long as I regularly get 8 hours min sleep and avoid all stimulants, this isn't a problem but sometimes stimulants or sleep deprivation are unavoidable. What could this be?