A soft reset can resolve issues like continuous resetting/rebooting, device crashing, freezing, device locking up, and keypad not responding.
This device has a non-removable battery. This process can be used to simulate a "battery pull" when the device is unresponsive, frozen, or doesn't power on.
In most cases, a soft reset won't affect data on the device, unless the battery is very low.
Press and hold the Volume down button (located on the right edge).
While continuing to hold Volume down, press and hold the Power button until the device powers off (approximately ten seconds) then release all buttons.
Pressing and holding the Power and Volume Down buttons captures a screenshot of the display. You may hear a shutter sound when this occurs. Continue to hold the Power and Volume Down buttons until the phone shuts down.