Device heating up is common is some situations. There is different apps on the Google Play Store you can obtain to monitor temps better from battery to device.
Also from my knowledge most devices have an emergency cut off that will deploy in the event the device gets too hot it will automatically power down. If you still feel the device is operating too extreme and its something you can easily duplicate it might be worth a trip to your local carrier/device store to have a tech experience it first hand. They may agree to replace it.