If you’re on a Mac, you can download Apple’s Configurator 2 App for the App Store and attempt to do recovery from it as well.

Try the following:

1. Uninstall and reinstall iTunes, then try restoring the iPhone again.
2. Boot the iPhone into DFU mode and try restoring it again.
3. Use another application to perform the restore, such as Apple Devices, or iSumsoft iOS Refixer.

If none of the above methods work, consider a hardware problem.

Here is a video that may help:https://www.youtube.com/watch?v=OScIw4eqlTI&t=135s

Hey, I've had the same problem before — it's super frustrating, I know.

Here's what you can try:

1. Use iTunes again with full restore

• Connect iPhone to computer

• Open iTunes

• Press: Volume Up → Volume Down → hold Power until you see recovery screen

• On your computer, choose Restore (not Update)

• Let it reinstall iOS (this will erase your data)

2. Try on a different computer

Sometimes iTunes just doesn't work right on one PC. Try using another computer if possible.

3. DFU mode (if recovery mode doesn’t work)

• Connect iPhone to computer

• Press Volume Up → Volume Down → hold Power until screen goes black

• Then: hold Power + Volume Down for 5 sec → release Power, keep holding Volume Down

• If screen stays black and iTunes detects your iPhone — you're in DFU mode

• Then restore in iTunes

Hope this helps!
References: 
https://support.apple.com/en-us/118106
https://www.tenorshare.com/fix-iphone/fix-iphone-stuck-in-recovery-mode.html

thx