BlackBerry Tour 9630

Lately I'm getting a terrible case of my phone randomly restarting. It started with roughly once a week, then continued to once every few days, then became unbearable at once a day. I decided to take it to Sprint and they upgraded my software, and it just made it worse: 12 times in 2 days. So I just got a refurb one. NO change. Just reset no more than 3 hours after getting this phone. Anyone else have this problem/a solution to it?