Getting this issue as well. It went away for some time until I had to reinstall Windows 11. I’ve done clean launches, repairs, reinstalls & driver checks as well as just about every other solution.
One thing I’ve noticed is that it typically only happens after I tab back in, and there’s a graphical ‘box’ flash that occurs in the middle of the screen and distorts the game as if some sort of program is launching or trying to take priority. It only lasts for half a second.
The only other things I might have in common is my computer is an HP, and I have McAfee and the Razer Synapse software up. Not sure if anyone is in the same boat there.
I really hope this is fixed in a reasonable time. It’s very clearly on Blizzard’s end. It doesn’t make the game unplayable, exactly, but it’s distracting enough and causes wrist fatigue from the mouse not snapping back to the center.