Sometimes i feel full of energy then all of a sudden so sleepy i can't keep my head up. what does this sound like?

?Sleep disorder: There could be many reasons, possibly low blood sugar, but a very specific sudden onset of sleepiness (and usually actually falling asleep with little warning) is narcolepsy. To sort that out you need to see a sleep specialist who will decide if you need a formal overnight sleep test and then the follow-up morning test to see if you still fall asleep quickly after good night's sleep, .