Make sure the graphics driver is updated. You could download the latest version, then reboot in safe mode, uninstall the old driver, then install the latest driver.
Also, run a Memtest check on your memory.
Check temperatures while stress-testing your system with Prime95 or other CPU-stressing program of your choice. If temps run too high, you could upgrade your cooling solution.
Finally, an upgrade of your PSU could help with system instability.