I had to think about this one - then I realised that, post 9/11, people won't get started for the same reason as me
I'm pretty sure that I got the bug after repeated cockpit visits on Dan(D)Air flights to Spanish holiday destinations as a kiddie. I vaguely remember wondering how fiddling with all those dials and switches got us from A to B... I definitely remember fighting with my brother to get the
aisle seat so I could see the flight deck (which ISTR you could at some phases of flight in the 70's).
I didn't think any more about it until I did a primitive 'Career Chooser' survey in the sixth form (punched cards and all) - airline pilot came out top, followed by computer programmer. As I was wearing glasses by then (and I believed pilots didn't wear glasses) I didn't give the flying a second (conscious) thought.
Mid-twenties I said to myself I would get a private licence before my 30th, but I got involved in that Internet stuff instead
Mid-thirties (OK - mid-to-late-thirties) I thought; I really am going to have a go at this before the big Four Oh.
And I did