Did you check the known issues thread to see if you’re having one of those problems? Known Technical Support Issues
Also, if it’s not software, it’s possible you’re overheating or losing connection with the GPU, RAM, or CPU. The Windows Event Viewer > Windows system logs can shed more light on any recent critical errors.
If none of this helps, you can provide a dxdiag and the other players and staff can look it over.
https://us.battle.net/support/en/article/12988