I am trying to help a friend and I haven’t run into this issue. iPhone 7 with IOS 11.2.
When opening an app or selecting an app from app switcher, we get prompted for the iTunes password. It does this randomly and not all the time. I thought there might be an issue with the OS so I performed a factory reinstall and set up the device as new, not restore. But same issue. When opening or selecting an app, we randomly get prompted for the iTunes password. He also has an iPad with the same Apple ID but he does not get prompted for the iTunes password.
Thanks for any help or suggestions.