ADHD

At this point, I just expect that my interest in a hobby will come and go as it pleases. I try to keep a bunch of hobbies and cycle between them, so I don't need to buy stuff every time my brain decides to switch gear.

A good one I've picked up recently is yoyoing. Originally, I just wanted to get an oldschool yoyo so I would have something to fidget with when I went for a walk.
I quickly learned though, that yoyos have gone through a bit of a renaissance lately, and there's a huge rabbit hole that you can jump into.
Getting started doesn't cost much (I recommend the K2 Crystal to start), and you can keep it with you to practice whenever the mood strikes.

Cross-stitching is also pretty good, but it's harder for me to sustain, especially on bigger projects.

You don't get into something, IMHO.

I hop back and forth between hobbies. Nothing really holds my interest for long unless there's a social element to it. So the first thing I do if I want to stick with something is fine a group to do it with. Make social commitments, so that you'll have an additional reason to do it. Like when I got really into hiking I had a group of 3 friends that I would meet every Wednesday for a training hike and then at least one weekend a month for an adventure hike. When I was rock climbing those same people started rock climbing with me and we met Monday, Wednesday, and Friday every week at the rock climbing gym and then did an outdoor climb about once a month.

Even with a group I eventually move on to something else. It's not that I get bored with the current hobby, it's that I find something new that totally enthralls me for about a month and then I find a new shiny hobby. So far my hobbies in no particular order are target shooting, scouting for hunting spots (even though I don't actually hunt), archery, rock climbing, backpacking, mountain biking, 3D printing, CAD, video games, reading, boating, fishing, FPV racing quadcopters, bodybuilding, amateur radio, & collecting baseball cards. That's obviously way too much recreation for a person with a full-time career, but I don't do it all at once except for bodybuilding which I try really hard to stick with. I'll get really into something for a month or two, then drop it for a year before coming back to it. It gets pretty expensive having so many hobbies, so I'm trying not to pick up any new ones. Thankfully there's a lot of crossover between some of them.

Start with things you've always wanted to do.

Always wanted to be an artist but can't draw well? Start sketching with no commitment to time or expectation of quality. If you find it's enjoyable, continue. If not, move on to something else. Maybe watch a few tutorials and find something in particular you want to learn to draw or a particular style you'd like to explore.

I'd just recommend not investing a lot of money in a hobby until you know you're inclined to stick with it. There are a lot of low cost ways to start exploring a hobby. Having a decent computer means you can download a lot of free software. Pencil and paper aren't expensive.

Find people who are already into a hobby you might want to pursue and talk to them. They might have tips and warnings. They might even have some old or extra equipment to get you started.

I find my interest waxes and wanes, and that the best approach is to find a few things you like and alternate between them as my mood shifts. For me, that's broad categories like reading, TV, video games, and YouTube.

I find I just have to listen to myself when I don't want to play anything, despite my friends playing, something I should be excited about, etc. Just have to quit for a month or two and not feel guilty about it. My passion for it will come back in time.

try to develop a routine around it.

set a start-time and adhere to it every day for a week or so. make sure to plan out ahead of time the VERY SPECIFIC actions that will set you along your goal for that particular day. you don't have to plan the entire activity but, for example, before you get out of bed lay with your eyes closed and CLEARLY VISUALIZE the first several steps you will take to practice guitar....

(10:30am)

1- open the blinds, let the sunlight in.

2- pull the amplifier over and power it up.

3- remember the tune from yesterday? hear it. how do those fingerings go again?

4- oh yeah, grab the music paper and pencil.

5-... and you're off!

only after you have a very clear idea of what, exactly, it looks like to get yourself going, do you attempt to begin. no plopping down and hoping for the best.

good luck!