What could be the possible cause for a LG 3200 to randomly turn off and restart itself?

For about the past month my phone has been randomly turning off and then restarting itself. It was fine because it only did it sometimes, i figured it was the battery. More recently it will completely turn itself off, and wont turn back on unless i take the battery out or will turn off in the middle of a call. I took it to a verizon wireless store and they said it was software but to take it to a repair center which I did today. The man that i talked to said that it was water damaged. There is no way that could have happened, I've never spilt anything on it. He said he could tell by a strip on my battery that was suppose to be black but has now turned an off white grayish color. I told him he was wrong because there was no way that could have happened. I took it to another verizon store and they told me that they thought the strip turned green when it was water damaged. Any help? I think that the repair center is wrong and I would like to prove them wrong so they will fix it. I dont have insurance and I'm not up for an upgrade until September. I think my model is a LG 3200. Please Help!