Are your joints bothering you when you try running? Maybe it's your breathing. Whatever the case, dedicate some of your first running attempts to figure out what it is and then figuring out how to make it better. If it's your joints, maybe you need to stretch better or even find shoes with more support. If it's your breathing, try to spend some time managing your breaths until you can keep them more even, but consider the possibility that you're pushing yourself too hard and that's the culprit.
I actually discovered that my biggest setback was breathing trouble because I didn't know how to properly breathe in and out in a manageable way while running. What has helped me is mouthing the words to whatever song is playing in my ears. It forces me to breathe at a more normal level so that I can get all the words in.