In General, whenever you open a screen in Pega, by default , the focus will be moved to the first editable field in the screen. It might be a field in the first column or the last column.
But you can use "set focus" action to set the auto focus to any other field in the screen when screen is loaded.
I am not sure if you can entirely disable the auto focus feature. Please try doing "set focus" on a read only field in the screen and see if works. I have not tried this, so not sure if it works but you can give it a try.