I have been having really sharp pains on the left side of the middle of my back.?

I was really just wondering if this is something serious or not. I don't like going to the Dr. unless I know exactly what is going on. It hits me about once a day and it goes away in about 5 seconds. Any ideas what this may be? It feels like a serious cramp or muscle pull. I am 32 years old and 6'4 230 lbs. I am obviously not skinny, but not severly overweight either. Any ideas would be appreciated. Thanks.