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. In most cases, a soft reset won't affect data on the device unless the battery is very low.
Press and hold the Power button on the right when viewed in portrait or the top left for landscape.
Tap Power Off then tap OK.
If the device is unresponsive/frozen, press and hold the Power button for approximately 10 seconds or until the device power cycles.