What Causes Intermittent Right-sided Pressure In Chest Area While Sitting?

Infrequently (usually while sitting) I feel pressure in the center to slightly right side of chest area. i am able to breathe and the pain usually subsides after 3-4 minutes. During the episode, I try to relax and slow my breathing and heart rate. I have no history (nor family history) of heart disease. I am a middle-aged man in very good shape. I have noticed that the episodes sometime come after eating a full meal, but not certain if this is causing the episode. Last night during an episode, I felt that I may have to throw up. While in the bathroom, the saliva in my mouth dripped for a constant minute of two. I did purposely did not force myself to throw up or spit; I just let the saliva drip out on its own. I would estimate the amount at 1/8 cup. Afterwards I felt no effects and no further pressure. Could this be some sort of digestive reflux? (There was no acid felt in my throat)