You may see the Reboot Slider appear on the screen, but you have to keep the power button pressed until the screen goes black. The moment you see the Apple logo appear, you can let go of the power button.
The iPhone should boot up normally and hopefully if the problem was minor, it should now be gone.
However, if the problem is not solved, then there are two other options you can try.
- Perform a System Reset.
- Head to the Service Center.
We suggest that you keep option no.2 as a last resort. Go to the service center only if the software reset does not solve the issue.
