Why does iCloud keep asking to verify my identity when starting up my computer?

Start my computer up to check email of whatever and iCloud displays a login screen. Where after I enter ID and Password, it requires a telephone to doubleverify. For many years I've had icloud and it never asked to verify my identity (when i did not start it up or intend to use it). Have not found anywhere to enter a persistent username/password. (as existed for 5 or 6 years).

IF iCloud keeps it up I will delete/remove it. Its very annoying when trying to do something and iCloud keeps insisting I verify who I am (ever time I startup MY OWN computer.

[Re-Titled by Moderator]