I hated cardio and running until I started viewing it as something that is toning my heart and making me healthier. The runners high is nice too
Just start and see how far you can go, and build from there. The walk-run-walk method is excellent too. If you look up a couch to 5k program it can guide you to help build endurance.
I used to be over 300 pounds and the thought of walking half a mile down the road to the park made me want to take a nap. Now I run 4 to 5 miles a day pushing my kids in their stroller (or use my elliptical if the weather doesn't allow outside)