On mobile devices a question may require scrolling in order to see all the possible answer choices. In order to have the quiz automatically scroll back up to the top after each answer selection to prevent people from loading a new question part-way down the page, you must embed your quiz using the javascript embed. 

To choose the javascript embed option, click "share & embed" or "publish" on your quiz and then choose the "javascript" option before copying the embed code and adding to your site.