I had the same issue with mine, it would keep rebooting itself about 3 times a day. Then one day it locked up on me and I had to shut it down by removing the battery. It would not turn back on at all. I called Verizon and they sent me out a new (refurb) phone. While waiting for the new phone I discovered that the contacts for the battery were a little messed up (not making full contact with the battery). I fixed those and it worked fine again. I still proceeded to send my old phone back (after doing a factory reset on it) just in case something else was wrong with it.
You may want to call Verizon tech support, they are pretty good about getting you a new phone when there are issues with your old one.
