Door closer problem ....door pops open

Question

I have a Jenn-Air side-by-side. My date of purchase was Aug. 2004. Since yesterday the fridge side door isn't staying closed after closing. I have to return to the door and push firmly...but I've never had to do this before. The Jenn-Air site mentions I might be having trouble with the door's closer but then doesn't outline what that is, just advises contacting a repair professional. Can you tell me? Can I fix this myself?