Why does my iPhone screen go away when it turns off and back on?

When my AT> 64gb iPhone 4s turns off, or dies, for some reason when I try to turn it back on, the phone itself turns on but the screen doesn't. Sometimes the screen will be a bright white, sometimes it will appear as if the LCD is cracked, and sometimes its just straight black. Eventually (like up to 12-15 hours later), I somehow manage to get it turned back on like regular, and it works fine (however occasionally, there's a white circle that surrounds the middle of the screen. Anyone have any clue what's going on with it? I'd just get the LCD replaced, but it only doesn't work when the phone turns off and back on, so i don't know if that would help at all.

Take it to the Apple Store, they can check to see what is wrong.