To soft reset (turn off, but dont delete data stored on the phone) your iPhone or iPad,

1. Press and hold the Sleep button.
2. Press and hold the Home button.
3. Hold both buttons until the screen turns off, and then turns back on.

This is a common practice used as a first step in many troubleshooting tutorials

Another thing you can try is to reset your settings.  To   do that, go to

1. Settings
2. Tap General
3. Tap Reset
4. Tap ‘Reset All Settings’