Turn off the engine. If it shifts with the engine off it's a good indication that your primary/drive clutch is sticking. You can replace the clutch with a new one but a better option is to have your clutch "tuned". On the other forum member MBdiagMan tunes clutches and there is also Griffin Performance that I think has an exchange service for their tuned clutches. MBDiaMan tuned my clutch last year and it's been bullet proof ever since and it's engagement and "gearing" transition is better than when it was new.