Are there any general MANUAL Shift problems with MB C-class

There's 1 fault that although I wouldn't call it common, I have seen a few times. i'm guessing the gear lever is either solid and won't go in/come out of gear or is just flopping around and feels disconnected. The gear selector works on a 3 rod system which link the gear stick to the gear box. The rods connect at each end to a fork and are held in place by a simple clip. Climb under the car and look at where the 3 rods connect to the 3 gear lever forks, chances are your missing a clip and a rod has come loose.

Im facing a problem with c180 2004 komp manual transmission, suddenly started refusing to enter gear 5 & 6 and reverse the lever feels loose. Wen the prob jus started I didn't continue driving please advise.

Mercedes-Benz manual gearboxes are generally bomb proof so my previous answer sounds like your best bet. I'm not too familiar with the 6 speed gear lever but I'm guessing that gears 5,6 and reverse are all on the same side of the gear knob.