A family of Microsoft word processing software products for creating web, email, and print documents.
Hi awalke9!
I have a very similar setup to yours, with a Lenovo laptop plugged into an external monitor and Office 365.
I had the same issue and couldn't figure out for the life of me what was causing it till you pointed out that it only occurred on the external monitor.
It took me a couple minutes, but the solution seems to be going into windows display settings (right-click on the desktop and select 'display') and make sure the scaling % is the same on both of your monitors.
This means you will lose a little but of screen real estate (only if you had to increase the scaling %), but the jerking should stop.
It seems that word just doesn't like different scaling and doesn't play well with scaling other than the one on the primary monitor :/