PUT IN A COOL SPOT- The first step is to keep your device away from sunlight because it can cause severe and permanent damage to the phone. Bring the phone inside which will make the phone come to a normal temperature.
STOP USING IT- Give the phone a break by putting it Aside for some time till it returns to its Normal Temperature could be one of the best ways to cool it down
TURN ON AIRPLANE MODE- Putting your iPhone in Airplane mode can help it cool down and can also enhances the battery life.
REMOVE THE CASE- In case of overheating, remove the cases and let them return to their normal temperature.
KEEP YOUR IPHONE UPDATED- Keeping your iPhone and all the apps updated will help the device function smoothly and consume the least energy.