What Causes Intermittent Pain In Left Side Of Chest?

I have been having sharp chest pains off and on all day, about a dozen in total. Pain is only on left side of chest, about 4 - 5 ribs from bottom. Pain is sharp and causes me to straighten up immediately, but only lasts a second and then is completely gone. No other symptoms at all, I feel great. Now 4 episodes in the last 15 minutes. What to do?