BobML500

I have a "new" ML 500. It's recently started stalling/stopping running. It stops, I wait for between 10 and 60 minutes, and it starts again. AFTER this happens, the check engine light comes on for a day or so, then goes off again.

I've read a couple of posts indicating Cam Position sensor, etc. Two questions: One: any ideas, and two: is it worth it to buy one of the diagnostic "tools" to view the codes?

Thanks!~

Bob