Don't worry about what anyone else us thinking. Everybody has to start somewhere and I know whenever I see someone who is new I think it's great that they're there and getting going. Certainly nobody I know would ever do anything but praise you for getting proactive, so why not give it a go. Before you know it you'll find that rather then exercising because you think you should you're actually looking forward to it and enjoying it.
Not sure where you live but have you heard of Park Run? It's on every Saturday and is a timed 5k. It's non-competitive, just you covering the 5k however you can. Some people run, others walk, some push buggies or take their dog! You could start by walking it and work your way up to running it. It's a fantastic community to be a part of, I love it. My son loves shouting 'go mummy' at me which us hilarious from the comfort of his pram!