I woke up this morning feeling fine, when I stood up I had shooting pains on left side of chest! It took my breathe away! I sat down after 30 seconds of it and as soon as I sat the pain was gone. I waited a minute and stood up again and the pain was back on left side of chest! I could stand up straight it hurt so bad. I walked back to my bedroom after standing for 60 seconds and laid down and the pain immediately went away?? I laid in bed for 5 or 10 mins doing some deep breathing and tried standing again and there was no pain? It's gone? What could this have been?? I had no other symptoms.