Sometimes there may be reasons where you need to reset your iPhone (without losing data).
This may be because your phone has become unresponsive, apps running slow, charging issues, the latest update not showing, etc.
To reset, press and hold both the Sleep/Wake and Home buttons for at least 10 seconds,until you see the Apple Logo. When the Apple logo appears, release both buttons.
The iPhone will now start up and should work as normal.