What are physical reasons that can cause a panic attack to occur once/month-good health, no trauma or history of panic for 40 years! coffee in am?

Puzzling: Having monthly panic attacks after 40 years without is a puzzle. In some people, caffeine and other stimulant use can certainly precipitate higher anxiety level and possibly panic. Your additional patient information indicates you also have insomnia, so you are not symptom-free otherwise. Please see your primary care doc for a personal review of these issues and your health.