I'll have to agree with you. If the clutch pack was worn out then the problem wouldn't correct itself. What you need to do is drop the pan and inspect it for debris. Usually this is a layer of dark particulate matter in the bottom of the pan. If things look okay change the filter and fluid. Don't forget to drain the torque converter. A complete fluid change will take about 7 quarts. If the problem comes back then it would likely be in the valve body. This is the hydralic brain that controls fluid flow to the various elements.