I'm autistic and I have a fetish for trains. Like, I look at the kind of train videos you can find on youtube of certain freight trains or sleek modern ones going by (I especially get off to Škoda 16ev).
I'm also into a lot of normal-er weird gooner stuff as well, but the train one is pretty unique. Sometimes certain computer UIs too but mostly trains.

I think it is because I have a strong enough fixation on them that it becomes sexual. It was also something I was looking at to calm my stress the first time I did it, it was just unusually arousing at that time and, then it started.

I believe >>144248 is mostly in the right here.