tightly freezes after 15-60 minutes on my PC

After 15-60 minutes of the game, the game freezes and you have to reboot. It makes me very nervous, I can not normally enjoy the game. What is the reason? If I select graphics control using the built-in CPU in the choice of controlling 3D parameters, crashes stop, but there is little FPS, just as unpleasant to play. Please help me.