Hey there, usually this is an issue with your graphics card. Can you:
- Make sure your graphics drivers are up to date
- If your graphics card software has "performance mode" or something, make sure that is enabled (or alternatively that "power-saving mode" is disabled)
- If you have two graphics cards (e.g. a laptop with an integrated card AND a discrete card for gaming) make sure the game is forced to run on the DISCRETE card, not the integrated one