Are you signing out each time you quit? Normally you should just stay signed in. This "sign in" is basically the same thing as what we used to call "activation". When you sign out of Photoshop or Creative Cloud, you are deactivating the products. The products will only run while activated.
If you are not signing out, are you doing any sort of system cleaning, or maybe such cleaning happens automatically while rebooting your computer (possibly because you are on a company network)? If so, this cleaning is also removing the files that track your sign in/activation and they need to be recreated. It's like a cookie on a web page that prevents you from having to log on each time. If the cookie is removed, you have to sign in again.
Thank you for your response. I've never "signed out" when quitting Photoshop nor have I done any sort of system cleaning. However, the problem has resolved itself and I no longer receive the "sign-in" notification.
As Emily Littella would say: "Never mind."