Lakeela, it sounds like a memory problem, not related to the game, especially if your reboot is random. I had a similar problem when I made my computer a while ago. After running for a couple hours, my computer would reboot, and the reboot would be unrelated to what I was doing at the time. I realize that your said your reboots occur in game, but I can't help but notice that I've had to deal with similar sounding problems
Try running another game to see if the reboot occurs in that one (Who knows, it could be related to memory usage). If your computer ever starts rebooting randomly, regardless of what you're doing, then replace your memory.
Mind, I could be completely wrong, but when I had that problem, it confused me to no end, and I would have liked advice like this. Either way, good luck at finding the solution.
/Stad