I've never seen this before, but it sounds annoying.
What browser are you using when you view this? Do you have any special widgets on the page in question? Is it always the same page or is it different pages every time? What is the page structure of the underlying page (like it has a layout grid with 4 columns, one of them has widget X in it)? Try opening the f12 browser console menu before you go to the page. Maybe there is an error in there indicating something with the javascript? My guess is that there is some element on the page with a hardcoded width that needs to be made responsive.
Apologies if this is more question than answer, but hopefully it gives you some places to check for clues.