What is a possible non heart attack cause of a quick sharp pain in the left chest/arm? can it be gas? other stomach issues?

Non-heart attack: Quick sharp pain in left chest and arm need not be from heart attack. It could be angina with out heart attack. Consult your physician. Other non-cardiac causes are pericarditis (inflammation of outer layer of heart), musculoskeletal pain, or neural pain.

Several: Musculoskeletal, lung, esophagus, stomach , pericardium can mimic.