Anxiety, gerd or heartburn in general (it’s literally called heartburn, this is more common than you’d think), and like a million other things.

I would get it with anxiety all the time before I was medicated, my doctor told me after my 3rd EKG that the pain from a heart attack really happens when you work it HARD. That might not be much for some people, but the Doc asked me if this happens often after physical activity at all.

My answer was no, and I hike, walk, go up stairs, do all that stuff and have no issue or pain with my heart. YMMV, and as I age I still take heart stuff seriously, but that reduced my anxiety around it significantly.