Restoring your device to default settings helps when the device crashes and resets itself or when apps freeze/hang or reset the device.
Performing these steps resets all system settings (e.g., ringtones, sound settings, display settings, etc.) back to their default values. Personal data such as downloaded apps and media (pictures, videos, music) aren't affected.
From a Home screen, navigate: Settings > Backup & reset.
Swipe left or right to access apps; steps apply to the default Home mode.
Tap Reset settings.
Tap Reset settings, to confirm.
If applicable, enter the PIN, password or pattern.