What Causes Pain And Weakness In The Upper Part Of The Body?

For the past few years I have had random episodes of pain and weakness in the upper part of my body. It will start in my shoulders and then arms and chest. It will last approximately 2 minutes and I will feel a little bad for a while afterward then ok. I discussed this with my cardiologist; he gave me a stress test and heart scans and said that he could not find anything. I am still having these episodes. I may get one 3 or 4 times a year or I may get an episode twice in one day. Since the beginning of this year I have had 4 episodes, two of those just recently in one day. What should I do to try to get to the bottom of this problem?