Re: How can I prevent ICloud from popping up on my IPhone and asking me to sign in?
Do you have 2 factor authentication enabled? Are you running any 3rd party software that is using iCloud? (I have 2FA active, and am running Fantastical). If both of these conditions are met, here's how to fix it:
Originally Posted by iMore Question
Apple started requiring application specific passwords/keys for iCloud access for apps that use iCloud data when 2 factor authentication is active. I first encountered this issue with Fantastical.
If you see this prompt, log into your iCloud account and create an app-specific password. Enter that new password in the prompt, and everything seems to be good now.
Using app-specific passwords
Originally Posted by Email From Apple Explaining This Issue