My Mac Pro keeps on going onto a blank screen every minute or so while using.

Mac Pro, or MacBook Pro. Laptops go off to conserve energy and energy saver/ power settings on their display.

Mac Pro desktops the screen may not receive a signal from the computer and need to be reconnected with a better cable.

Sophisticated tasks may overheat the machine and cause the machine to completely power off, requiring a restart from the power button. If that happens, and the machine is under warranty, call AppleCare to have the machine's internals investigated. But generally that problem only happens while actually acting on the computer itself. inactivity otherwise is a good reason for powering off.