Is having off and on left side jaw pain a symptom of a heart attack?

It can be: It's very possible. It is more likely related to something associated with the jaw, but there is a chance that it is pain associated with the heart. Get it checked out.

Possible: It is impossible to tell without an examination. If you have been having this symptom for any length of time i would strongly advise seeking medical and then a dental examination thereafter once an mi is ruled out.

Possible: Possible, especially if associated with exercise. Rule out a heart problem by seeing your MD ASAP. Then see orals surgeon about jaw pain.