Start out slow. My doctor tells me walking is as good as running. Try increasing after a week or so to a mile. If it's too much back off a little on distance (don't stop though).
You may have to push yourself a little. The first time I ran 2 miles as an adult, I threw up. First time I ran 5 miles, I almost passed out. But, I was pushing my body beyond its limits.
Honestly time keeps me from exercising, but I still manage 2 miles about 3 times a week. Oh and I don't do track running, I just measured out a part of town that is about 2 miles and run/walk that.
If you're cramping continues, eat half a banana afterwards, or just take potassium pills. They help with cramping. I cramp after long rounds at times still.