I had my phone (HTC Titan) on and sitting on the start menu (I was looking over the apps I had installed). Without warning, my phone just shut off. When I restarted, it would load up my home screen and then almost immediately (1-2 seconds) shut off again. This happened several times in a row. I finally got it to come up by removing the back cover (meaning it got no signal). At this point it stayed on no problem. When I replaced the cover it reconnected and was fine at first but as soon as it connected to 3G it shut down again.