I have been having this problem since around a week ago. It first manifested itself on my iPhone X. I would get the prompt at least once a day when opening an app. (The apps that triggered the prompts have been different.) I tried signing out of the iTunes Store and iCloud, rebooting, and signing back in again; but that did not resolve it.
Then a few days later it started happening on my iPhone 8 Plus. Then, yesterday, it happened on my Apple TV 4K.
Just today it has happened at least five times between my two iPhones. The iPhone X and Apple TV are running the latest betas, but the iPhone 8 is running 10.3 GM, so it is not a beta issue.
It has not yet happened on my iPad Pro, and I hope it remains that way. This is becoming very frustrating.
Like @
NameUndecided, I, too, thought Netflix may have been triggering the prompt, but I have signed out of Netflix on all my devices, and it is still happening. I will try completely deleting the app.