Entering recovery mode can help if you're having trouble updating or restoring your iPhone over the air. For example, if the screen shows the Apple logo for several minutes but no progress bar appears, you can try putting the device in recovery mode and restoring it with iTunes. Here's how it works.
Using the cable that came with your iPhone, connect the device to a computer that has the latest version of iTunes installed.
Launch iTunes on your Mac or PC.
With the iPhone connected, force restart it with the following steps, but don't release the buttons when you see the Apple logo. Instead, wait until the recovery mode screen appears.
Press and quickly release the Volume Up button.
Press and quickly release the Volume Down button.
Press and hold the Side button until you see the recovery mode screen with the "Connect to iTunes" screen, then release it.
Select your device in iTunes.
You should see a message in iTunes saying that your iPhone is in Recovery Mode. You'll then be given options to update or restore your iPhone’s software.
How to Exit Recovery Mode on your iPhone
Simply press and hold the Side button until the "Connect to iTunes" screen disappears, and your iPhone should reboot back into iOS.