Everything was running perfect for months without any problems. Yesterday woke it from sleep but the touch screen wasn't responding (sleep and home buttons were). I force shut it down it by holding the sleep button so I could restart it. Now when I try to start it back up, it displays the Apple logo for about 10 seconds and turns off completely. I can't seem to enter DFU mode as it doesn't stay powered on for long enough to let me do that. Tried turning it on while its both plugged in and not. No change. Please advise.