When I lie down for awhile, or when I first get up in the morning, I get a weird rattling/vibration upon taking breaths in. It only happens when I take a deep breath, at the end of the breath, and goes away after a few breaths or if I cough. Its been going on for a few weeks, and really starting to worry me that it is fluid in my lungs or something more serious!!

Anyone ever experience anything like this? I can exercise without this sensation and have no troubles working out at all.