I am having the same issue!
I was using an app and was attempting to close it because it was glitchy and delete photos to clear more storage. All of a sudden the grey spinning wheel appeared. After a while, nothing seemed to resolve so I tried to restart it and has been stuck in reboot loop. Plugged it into the computer to see if I can update that way, (as instructed by Apple support), but could not update. This is the message that appeared: "The iPhone “iPhone” could not be updated. An unknown error occurred (1110). 06A1.0456"
I went to Genius Bar today, they basically told me that I have to try 3rd party data extraction (which costs $800+ minimum with no guarantees of recovery), or wait for a new iOS to see if this issue resolves (who knows when that would be with these update files being massive), or I factory reset it (which means that I lose a year's worth of my baby's photos and videos).
I'm frustrated that I can't get access to simply clear off some stuff that's been stored on the phone so I can have a new update and now it's simply bricked and stuck in this restart loop.