When I was around 14. But I don't really count times before the current one because I didn't even plan it. I wanted to impulsively do it (jumping) and then something would always stop me and I wouldn't.
Now I'm researching how to properly do it, exploring all the options and I want to make plans. It's because after some time in therapy and some events in my life, I can feel my emotions better and I feel agency and some freedom... So that was the first and only thing on my mind after I felt freedom, agency... It sounds really weird, but it's what's happened.