This applies to my current environment on an HP laptop (FF 72.0.1; Win10 build 18362), but it's been like this for six months or more, after not being like this before.

I restart my work computer - again, an HP laptop - at the end of every workday, so it's fresh the next morning.

My FF browser is set to load with the same tabs, in the same two windows, as it had when I exited the night before.

Without fail, as the second browser window loads - it has a web interface for my google pixel text messages as the active tab - it "pushes to the front," even though I might be working in the other browser window, or on a Word document. My active session, whatever it is, gets "bumped" by this window pushing to the front.

I've never seen this behavior on any other computer. And my work computer was configured when I got it with a copy of my home computer's Firefox profile, and my home computer runs same Win10 build, same FF browser, same two windows, and starts on the same tabs in those two windows.

Any idea what causes this "push to the front" behavior?