iphone just suddenly died

i was using my iphone while watching TV tonight and set it down on the coffee table. when i picked it back up, it was just completely dead. screen was dead, it wouldn't turn back on. when i plug it into my Mac it just does nothing. pushing buttons does nothing. it is just as if it were there one minute and gone the next for no reason! if it had been plugged in or something, i'd suspect a power surge. but it was just sitting there, and no more than 10 minutes had passed since i last used it with no trouble. any clues anybody?!