I vaguely remember having a neon green colored bike with detachable training wheels as a kid. I wasn't particularly obsessed with it but it was something I occasionally did. At a certain point, I stopped riding around my preteen years once I grew out of it.
A few years ago, I saw a friend hop on a bikeshare (a Citibike as I live in New York) after a work meeting and I remembered being super impressed at how easily she just jumped on and sped away. It would be another 2-3 years later when I decided to try it myself. I committed to a membership and took the 45lb+ bike along the waterfront path and it was pretty horrifying but exhilarating and having not rode a bike in 10+ years save a rickety $100 Craigslist bike I bought in grad school a few years before that I rode all of 3 times before selling it to a friend, it took a little re-adjusting but as they say, like riding a bike.
A year or year and a half later I bought a Brompton (as a friend advocated for one) and I rode that thing for 2-3 years (I also learned a lot of things to avoid on it as I've had plenty of literal scrapes on it) but that and Citibikes got me comfortable with riding in the city. I found an old Ti frame at a jumble sale and built it up to be a fixie (since I was curious) but very quickly that got stolen. When building that Ti bike, I ended up watching a lot of how-to videos and also encountered a lot of road cycling videos which got me curious. I quickly became tired of hauling my bikes up my walkup (I also briefly had an ebike which I later sold) and the Ti bike was oddly never that light anyway. I ended up getting a road bike and have never looked back.
I was in my early 30s and while not fat, I was never particularly fit. Nothing interested me athletically and I hated running or anything cardio. I quit gym class as soon as I could and I always associated physical education with humiliation and discomfort. Somehow 20 years later, cycling got me.