Originally Posted by
raphie Me too! It's driving me crazy. I have signed in and out, still occurring

When you get a pop up asking for credentials, have you tried entering the info it requests? It could be iCloud trying to do a back up. If your phone is plugged in and asleep, then you pick it up and open it, you may have done so right when iCloud was about to back up. Then it asks for ID verification. Enter the info when asked. Then go to Settings > iCloud > and do a manual back up. As soon as it's done, do a hard reset.
Hold the top or side power/sleep button and the home button at the same time until the Apple logo appears, then release.
Let us know if that works or not.