Thought this might be a fun discussion ...
I recently had to drive a long-ish car journey, and, as usual, my mind worked on writing and plot ideas. The normal sorts of things for me: kidnapping, murder, theft, perilous journeys, how the magic system works, whether two of my secondary characters are actually a good match for each other, how many different ways I could think of to express apprehension ... and a lot more besides.
I then wondered if other writers do the same sort of thing? Would love to know.
Also, what on earth do non-writers think about? I can spend hours of time plotting stories and mapping out worlds in my head!