Annoying "You've been away!" popup

While working on challenges in the Python 3 course I consistently get at regular intervals (every…±5 minutes?) a pop-up which you can see below. It doesn’t matter whether I’m constantly typing and in fact being active on the page, it will always pop-up!?
And even more annoying…it will clear the right side of the screen with the output code!?
This can’t be normal…any ideas how to stop this annoyance?
For now I’ve only used Chrome but if you think it’s browser-related, I can try another browser.

You've been away!