hallo do u think u can find out what's wrong with my iPod touch?

okay so I was just clicking a few pictures and I locked the screen. When I tried to turn it on again I can't! It just died out on me! It's happened to me before. I did nothing, just locked the screen, and for a reason I do not understand (or know of), my iPod doesn't turn back on! Do u think u know what the problem may be?