If laptop you need to have on a flat hard surface to allow airflow.
If desktop it would be best to download a hardware monitoring tool so you can see the temperatures of your processor, graphics card and ram. After playing some games check the temp and if the graphics card or processor is extremely high (80 degrees +)
If your processor is overheating you may need to reapply thermal paste to the processor so the heatsink of the processor cooler is making contact. If neither of these work, try installing a new fan or just having the side of the case off permanently.