I think starting anywhere is such a great thing especially when you have the goal of doing a 5K in mind. I'm trying to get my mom to walk with me in the evenings but she just broke her toe while we were moving this past week so that might be stalled a bit... :/ anyways you can totally do it!! You're already doing so great!
Its funny you say that because that is the very reason that I decided to try running instead of exercising on the elliptical. I realized I just wasn't getting an intense enough workout anymore even when I tried different intensities, interval training, and even the cross country program. I just didn't feel like it was working for me anymore. It's hard, but it's mental. Once you've gone .2 miles, you know your body can already do it so why not do the same thing again and push it to .4 of a mile? It's thoughts like those that get me through my runs right now. You should start your workout on the treadmill! It might be the one cardio machine you'll use...