If you are displaying all questions without any page break or skip logic or display logic then add a time and auto-advance after 15 seconds.

Unfortunately, I need the questions within a block to be on separate pages.

Another approach could be using JQuery.
Use the code to capture the time for whichever block, and auto advance when crossed 15 seconds.

That sounds like the way to go. But given Qualtrics' layout, I don't know where to put in the Javascript that applies to the whole block. Also, is the block name the one I assigned or is there a default one that is hidden somewhere else?