I'm 27 and got sharp pains in the left side of my chest. it only lasted about 10 seconds but was very scary . what could this be?

Muscle spasms: Fleeting pains that don't come back are often from muscle spasms in the intercostal muscles.

Multiple low risk po: The fact that the pain went away is good. The possibilities are most likely trapped gas in your upper abdomen or a musculoskeletal non-serious problem. Less likely would be a cardiac or pulmonary problem. See your physician.