I had this phone since Dec. 2013 around Christmas, a couple of weeks after I gotten the phone it started to shut itself down and turning back on itself. I thought it was just straight talk updating the phone all the time. Sometimes 2 to 3 times a day. a couple of months ago it started to do so while I was texting and now a few weeks ago it will shut down while I am on the phone. I know it's not the battery, the battery been fully charged while it shut itself down and back on.
I too have had this problem. I'll be in the middle of anything and it shuts down and then powers up by its self a sec later.
I've been having the same problem. It does it about once a day, sometimes more. There's no reason for it that I can see