janelle,
i have had a similar experience. i don't have an answer for you but i have had this happen several times over the last year and it has slowly stopped happening. i think the last time it happened was about 2 months ago. the first few months i was having shortness of breath, it was coming almost every day. i stopped worrying about it after i became used to it and eventually it just happened less and less. i honestly believe this is another anxiety-related illness. it sounds to me like you are in a state of stress which causes you to breath more shallow during the day without you realizing it. your body is probably having moments of catching up where it decides you need to take in more air. i also took up breathing exercises, since i know that improper breathing can lead to low oxygen saturation which is the perfect environment for cancer and other illnesses to thrive.
imagine a square. as you visualize one corner of the square, begin inhaling, counting to four, and imagining your gaze going across the top side of the square. at the next corner, exhale slowly while counting to six and imagining your gaze reaching the bottom corner of the square. now inhale again while counting to 4 and gazing along the bottom edge of the square.
imagining the square helps you to see a start and end point to each breath as it cycles, and the counting helps you to retain a relative image with two identical inhales and exhales. just spend a few minutes each day doing this and make a point to breathe more effectively throughout your day.
i wouldn't consider periodic shortness of breathe to be an indicator of anything. unless it's constant and getting worse over time with pain or other symptoms, rest easy and don't get to overwhelmed by the sensation. don't wait for it to happen or try to prepare for it, but if it does happen, then lay down, put one hand on your stomach, and one on your chest, and feel the air going in and out as you practice the breathing exercise.
best of luck.
take care
-destiny
ps. i think you have to select a health issues category first, and then there should be a blue "start a thread" button up near the top left of the page. if that's not right, it might say "post a question" near the same area of the page???