I consume one cup of decaf coffee 3 times a week from one of the coffee shops.most of the time i feel fine but 1 out of 20 times maybe i feel jittery,short of breath,dizzy,lightheaded & anxious after drinking it. what could be making that difference?

It's possible that you've mistakenly been served strong caffeinated coffee. Either that or you're occasionally experiencing an anxiety reaction or cardiac arrhythmia. Check your pulse should such symptoms occur in the future. See your MD as needed.

Agree with Dr Colantino, as almost certainly, your reactions are due to an increased amount of caffeine in your coffee. Be assertive and request proof that your decaf coffee order is prepared as ordered and not inadvertently replaced by a regular coffee.

Caffeine can affect different people in different ways. If your symptoms are related to the coffee, most likely you’ve accidentally been given regular coffee on those occasions not decaf. There is also the possibility that this has nothing to do with the coffee and the coffee is a red herring. I would stop the coffee. If your symptoms continue, see your internist