What causes this weird indi"chest"ion?

Quite often, I will get a peculiar type of indigestion. No stomach ache, no acid reflux or heartburn. I just get chest pain, like in my heart area. I feel pain and pressure between my heart and my left shoulder, very high. The pain radiates down my left arm and up to my jaw, just like cardiac pain. But then I'll let out a big burp, and the burp feels like it's coming directly from my left clavicle area, near my heart. I feel instant relief, so I know it's not cardiac. It can happen several times a day. Severe chest pain relieved by a burp that comes from very high in my chest. What could it be??