I'd suggest you Clear your devices system cache. If that fails try to boot it up in safe mode, see if it still overheats and if it does just delete every other new app you have recently downloaded to find the culprit. The final resort will be to back up and factory reset the device.
Keep in mind this is a relatively old device and will find it harder to deal with modern apps.🙏 Hope this helps
Perhaps a hardware issue. The hardware may be reporting false temperature reading.. If your phone is cool but you still get the overheating message, send your phone for repair. It's likely a hardware problem.
