The iOS 17.3 iPhone update is stuck in a loop

See this article.

If your iPhone or iPad won't update - Apple Support

You have asked us to guess everything about your scenario. Among the things we don’t know:

• What you tried
• What you saw
• What worked
• What failed
• Error messages
• Steps you tried in the article I linked above
• Mac operating system name and version
• iTunes version (if applicable)

I have same problem with 2nd gen IPad Pro 12.3. I have tried several times to install the update. I have reset the iPad, deleted everything and started the iPad like new, with iOS 15.

it still won’t take the update. It hangs during install?

A lot more info is needed from you, as requested above.