Diamond Resets by itself help!!!!!!

i have just recently gotten a new diamond. Sometimes the phone works just fine. But sometimes i answer a phone call, and my phone just reboots. This problem is getting very annoying. Also sometimes i try to make a call and it says connected, but the person never gets the call to them. This is very frustrating. I dunno if this is hardware related, im using the stock sprint rom, and i did clear storage 2 times to try to fix it, and its not working.