The good news is that (other than the pain) it is completely harmless.
The way it always felt to me is like someone wrapped a small wire around something tender in my chest, and if I tried to breathe or straighten my posture, they would yank on it. I’d get it anywhere from a couple times a week to once a month. Then one day in my mid-30s it just stopped.
From what I understand this is relatively common. I was so grateful for the person on reddit who dropped this nugget of wisdom several years ago. It was nice to know I wasn’t dying or whatever.
It means do you sit or lie around most of the day. Do you have an office job where you sit at a computer all day then go home and play on your phone or whatever until you go to bed? That’s sedentary. If you exercise that’s good but if it’s something like a radiculopathy you’d benefit from seeing a physical therapist who can target the section of the back that is impacted (though you may need to start with primary care or orthopedic and mri). If it’s the other stuff treatment is generally medications and varies from stuff like NSAIDs or proton pump inhibitors (though if it’s gerd and you treat with NSAIDs that may worsen things)
Basically go see a doctor