If your iPhone becomes unresponsive try these easy steps first.
If you are still experiencing problems after this the next step would be to try a Restore through iTunes.
Connect iPhone to a high-power USB port, such as the one on your computer, or use your iPhone AC adapter. If either of these screens are present, keep iPhone connected so it continues charging.
- Don’t use the USB port on your keyboard because it is a low-power port and iPhone will not charge.
- If you see the red part of the battery image flash three times and then the screen goes black, it means that iPhone is not receiving power to charge.
- If the iPhone battery is extremely low on power, the display may be blank for up to two minutes before one of the low-battery images appears
To restart iPhone, first turn iPhone off by pressing and holding the Sleep/Wake button until a red slider appears. Slide your finger across the slider and iPhone will turn off after a few moments.
Next, turn iPhone on by pressing and holding the Sleep/Wake button until the Apple logo appears.
Is iPhone not responding? To reset iPhone, press and hold the Sleep/Wake button and the Home button at the same time for at least 10 seconds, until the Apple logo appears.
To restore your iPhone, first make sure you are using the latest version of iTunes.
Next, connect iPhone. In the left column under Devices, click on your iPhone, then click on Restore in the Summary tab.
For more information about backing up, updating, and restoring your iPhone software, see this article