A soft reset (powering 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.
Power the device off. Press and hold the Power button (located on the front) until the Power button LED light shuts off. If unable to power the device off, remove then re-insert the battery.
Power the device on. Press and hold the Power button until the Power button LED is solid green.