The phone will get warm when it is being heavily used (such as streaming video, GPS navigation, charging, or other functions/apps continuously running in the background. Some heat dissipation may occur when this occurs making the phone feel very warm. This is normal.
To test to see if an application running in the background is causing this issue, try using the phone in ” Safe mode”. When safe mode is enabled, only the minimum applications are loaded when the phone is started. No user-added applications can be run when in this mode.
To enable safe mode:
With the phone on, press the power button until the pop-up window displays. Tap and hold the “Power off” icon and the phone will prompt to confirm if you wish to reboot into safe mode. Once confirmed, the phone will reboot with minimum drivers and show “Safe mode” at the bottom of the screen.