iPhone that becomes unresponsive due to a buggy app, system error or an undetermined malfunction may not allow you to follow the normal iPhone shutdown procedure. However, in most cases you can still shut it down using the "hard reset" method, after which a simple restart should fix a problem with an outdated app or system software. Upon restarting your iPhone, check for any available updates for both the iOS software and apps installed on your device, as software and app updates can often help resolve iPhone problems.
Press and hold the "Sleep/Wake" button and swipe the red "Slide to Power Off" slider when it appears. Press the "Home" button while holding the "Sleep/Wake" button if the slider doesn't appear. Hold both buttons for at least 10 seconds until the Apple logo appears.
Tap the "App Store" icon on your iPhone, and then select the "Updates" tab.
Tap "Update All," and then provide your Apple ID and password to automatically install any available updates.
Tap the "Settings" app, select "General," and then choose "Software Update."
Connect your iPhone to a power source, and then select the "Download" button, if available.