Hi we have 2 thunderbolts and my wifes has had several times where she went to check the phone for a message or to send a message and it was turned off. No it was not in sleep mode, power button was not pressed by accident or anything like that, the the power button had to be held until it turned back on and went through the boot up. this has happened several times (3-5) on her's and once on mine. My wife texted me this morning that it happened again she woke up went to take phone off charger cord we put them on every night and her's was off when she treid to go to home screen. we have also experienced sevral reboots. Reboots I can deal with but not the shut offs our daughter has asthma and we need to be able to be reached in an emergency. Has anyone else exerienced this issue? It has never been becuase of a low battery we both have never used it enough to drain battery any less than 35% in a day. we are new to android and came over from BB we both love the phones speed and os, the battery could be better for heavier use.