I'm not a slightly built person either, the first time I ran I only ran for a little over 6 months, I was a Jim Fixx devotee who died of a massive MI while running, that helped changed my mind, I had gotten up to about 30-35 miles a day and really enjoyed it but work and other things also got in the way.
Since then I've run off and on, or walked, the thing I like about it is once you get into the zone you just seem to glide almost effortlessly, and it also regulates my appetite, I actually eat less when I run.
I never ran enough to hurt my knees, I was pretty light back the though, I'm not as light now as I was so I'm taking it easy and building up. It's not really easy to run in this city though, lots of cars and intersecting streets. I run to the next main street and back, about two miles, that's enough for now. I do feel a lot better since I started again though, we could only go out for an hour a day during the pandemic so I couldn't wait to do some kind of exercise.