Soft reset can resolve issues like continuous resetting/rebooting, device crashing, freezing, won't ring or vibrate, can't make or receive calls, device locks up, and keypad doesn't respond.
A soft reset (turning the device off then back on) is similar to restarting a desktop computer and is one of the first steps in troubleshooting a device. A soft reset won't affect data on the device.
Press and hold the Power button to power off the device. Once the 'slide down to power off' message appears, swipe down then allow several seconds for the device to power off. If the device does not power off, press and hold the Power+Volume down buttons until the device powers off then release (approximately 10 seconds).
If necessary, press and hold the Power button to power on the device.