When I press keyboard arrow keys the mouse cursor also moves. This started happening after some recent updates / reboots. Searched some and the problem is MS Paint is open. After I close MS Paint the problem stops. I find this odd because I use MS Paint often and have surely had it open before when I used the arrow keys. Either way, now that I closed Paint, the arrow keys no longer move mouse pointer.
I checked Ease of Access > Mouse and nothing was enabled / on.