2 Solutions to try :If the phone won't turn on after removing the battery due to freezing.
1. Remove the battery and press the power button for 20 seconds
2. Connect the phone a live charger without the battery and press the power button for 15 seconds.
3. Put the battery back while still connected to the charger.
4. Wait for at least 5 minutes before turning on the phone.
If this solution does not bring back your phone then you might have a corrupted firmware. Please let us know.