My son has a door fetish.
He's had it since he was old enough to walk, when he would head straight to the kitchen, whereever we were, and slam the cupboard doors that were low enough for him to get his little mits on. He moved on to bigger and better doors, where he only caught his fingers once. When he was potty training, you couldn't keep him out of public restrooms, compelled as he was to check out each and every stall. Now he has left behind regular swinging doors (except for the obsession with closing them after he's gone through them), and is completely and utterly fascinated with mechanical doors - doors that close on busses, trains, automatic doors in shopping areas, etc. I would worry, if I thought it would help. But I do wonder where it comes from. Is it because I had to have an emergency C-section and he didn't get "closure"? (I am mostly kidding, there). Is it because he has a highly technical brain? Is he headed for the couch in later years? Is he a walking, talking, singing artistic metaphor for life and passage? Or is it something that will pass when he hits his teen years and discovers girls and drugs and porn?
I can't even think about that last one. I will need to be wrapped tightly, with loud music to block the noise when he hits his teen years.
For now, I choose to think of it as his genius curiosity.