What Causes Rattling Sound From The Esophagus Upon Breathing?

I have an annoying rattling sound coming from my esophagus area that requires that I essentially breath it out on a regular basis. Somewhat annoying during the night trying to sleep. I m not coughing. I simply exhale with force and the phlegm moves up and I swallow. This goes on constantly throughout the day and night. At night I have more of a difficult time laying on my right side as compared with my left. It wakes me up throughout the night. Any thoughts on what this might be? Thanks John