if it is verizon you should take it back, they will give you a new one. i also have an lg, it's a chocolate, but sometimes mine does it, i just take it back. it is probably something in the technology that isn't right.
it means the ribbon in the pull out keyboard is worn out, happens at about 4 to 6 months old. it causes the phone to power off all the time. this phone is a piece of crap. ive had 2 of them and the same problem with both. updated to a blackberry curve and now im happy!