The gym never worked for me. Like you I just can't get myself to go someplace to exercise, it seems like an insurmountable job. What really helped me 13 years ago was doing something I could do easily. I want to stress that exercise doesn't have to be a fixed gym routine. It doesn't have to be a planned out walk where you time and benchmark your progress. It can just be a stroll around your neighborhood, I like walking around and mapping with StreetComplete. Sometimes I'll even bring my laptop and do some micromapping with josm.

Personally I find that I get way too competitive if I track my workouts. I bike for an hour around 3-4 times per week. I don't know which days I do it, I don't know how fast I go. I just go and ride wherever i feel like, take whatever turns I feel like. Usually my rides end up about an hour long before I get bored, but sometimes (especially in the summer months) they turn into 4 hours.

You'll find that your body changes drastically. Most people (me included) has this idea that the body will adapt relatively quickly. Maybe a couple of months. I've found that my body kept getting stronger and more efficient well into the 5th year of doing exercise. You'll be surprised at how much your body can actually do, and how much of that training carries over, even when you let it slip for a couple of weeks (or you break your ankle and have to pause for 2 months).

Then of course there's the fantastic extra benefit that any additional activity you may find interesting gets much easier once you're body is already tuned. I recently picked up skate boarding, something I wanted to do as a kid but never had the physical ability to participate in.