gear box ecu

So I've recently got a C350 CDI and noticed when I'm driving then slowing down, it shudders when the car gets down to 3rd, 2nd gears before stopping, not massively, but noticeably. Almost like it's about to stall if it were a manual. Normal behaviour for a Merc automatic?

I am looking for any suggestions as to a fault I encountered today. On starting the car and selecting R I moved a metre and heard a clunking noise and moved no further. Selecting D or R sees no engagment and the car remains in one spot. There are no indications on the dash of any fault...