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 momentarily hold the Power button.
Select Power off. If the device isn't responding, continue holding power button for 7 to 10 seconds to force a shut down.
Press and hold the Power button to power on the device.