rewind50

when accelerating and the car is about to shift gears it lags and makes a rock in a tin can sound, does anyone know what this could be and why?

thanks in advance

_AMG_

does this occur in manual mode?

rewind50

never in manual mode
mostly in cruise and sport mode

any idea what it could be?

_AMG_

I have heard in some cases when switching between C/S/M mode while driving, the transmission would make a clunk/metal sound. I would take it to the dealer to be on the safe side.
Lag in gear changes usually occurs when the engine is still cold and hasn't fully warmed up yet.