Look for a couple of things-
There's almost certainly an aspect ratio compensation factor in the monitor's auto-adjust. They won't call it that, but it rearranges individual pixels from a 4X3 ratio to one corresponding to the shape of the NATIVE RESOLUTION of your monitor. Run that. It looks like your monitor shakes a bit and settles down.
If that doesn't do it, check the monitor manual for any hard settings that will result in the same thing. Its NOT a setting you change from your keyboard- its a monitor menu change. Use buttons on the monitor. I just experimented 'til I found the right settings on mine.
3rd thing to look into- in your screen resolution settings (right-click mouse on desktop and select properties) . Choose any setting that DOESN'T show a ratio of 4x3 (your old monitor aspect ratio). For instance 1024X768: 3/4ths of 1024 is 768. Find out your monitor's native resoution, and choose a screen resolution that has the same ratio. This should round circles and square squares.
Post back with your final solution- there's likely lots of folks " just living with it " !
Good luck!