Sanyo MM-8300

Ok I've had this phone for a few months, haven't had any problems with it thus far. last night, i had just sent a text message, set the phone on the counter and thirty seconds later come back to check it, only to realize that it had shut itself off. thinking this was a little strange, i tried turning it back on with the power button, to no avail. i've tried everything... taking the battery out, plugging it in with 2 types of chargers, holding the power button for a minute, but nothing has worked. what should i do!?!?!?!? it hasn't gotten wet, and i haven't dropped it recently.