Apple logo with progress bar after updating or restoring iPhone, iPad, or iPod touch
After you update, restore from a backup, or erase your iPhone, iPad, or iPod touch, your device displays the Apple logo with a progress bar.

The progress bar may move slowly or appear static, but it's important to let the device complete the process, which can vary in duration based on the number of files and the type of operation being performed. In some cases, you may see the progress bar complete, then start again.
Try any of the following suggestions:
If your device appears on your computer, you can configure sync options, and you can sync content, the process is complete. Leave your device connected to your computer and wait for the migration process to finish.
For over-the-air updates, ensure that the device is connected to a power source to prevent it from running out of power during the update.
If the update seems stuck, pressing a button may help; if an 'updating' message appears, the update is still ongoing.
Get help
If the update or restore never completes or your device is unresponsive, force your device to restart.
If your device still displays the Apple logo with a progress bar, you might need service. Get service