hint2

Occasionally, my C320 Coupe up-shift from 2nd to 3rd very slowly. I feel the gear is disengaged and the rpm dropped very slowly then engaged to 3rd gear. I think because no gear was engaged when the rpm was dropping, I felt no power inbetween. I got a harsh feeling when the 3rd gear is engaged. This made the shifting not very smooth. It only happened in 2-3 shifting and it didn't happen all the time, only in moderate acceleration. It never happened when I used touch shift. Other shiftings are very quick, I can feel the power right after the gear is disengaged. Is this normal? Is it something related to gear ratio? Please help. Thanks.