How to start doing cardio gradually?

I want to start running in the mornings or do some type of cardio. I tried this a couple summers ago and ended up getting really sick, and I don't know if I was pushing myself too hard or what.. but it scared me enough to quit it for awhile. However, I still feel as though it would be good for me and for my body. I'm wondering if there's a safer way to start running or jogging.. so any tips, opinions, comments, concerns are greatly appreciated!! :)