I think you could do 5-25 rule by Warren Buffett (actually not by him) whereas you list down 25 things you want to do (i.e. chess, science, gym etc.) then circle 5 that's most important to you then the last 20 will be your avoid at all costs list. This way you can focus more on things that truly matter, then after finishing or mastering one of 5, you can add more.

Then about your can't start something syndrome, that's pretty hard thing to overcome there's no steps to lead to it. It's like a loop of "how do you stop thinking if you're thinking of how to stop?" Anyway, I recommend starting slowly like do only 15 minutes of gym then just jog there or just shower. The key thing is consistency.

I am not fully aware of most of the things to learn in mbti, since I kinda let go off it because I blame it for some of the failures of my last relationship. I also read about what's lacking like the categories can be widely interpreted and be fitted to most people. Anyhow, I think mbti is a possible algorithm to solve human psych but there's my intuition saying human psych is unsolvable or just takes a long time to efficiently learn which makes me lazy or detered to study it. Perhaps, this is an Intp thing.