It's happened twice in the last few days. I've never had it happen before. I put the phone in my pocket or whatever, and then next time I go to use it, it's dead as doornail. I did some googling and found out that doing a hard boot might bring it back to life - and it has.
But, it said that that probably means it's a software problem. So, is there anything simple I can do - or is it time for a new phone?