Originally Posted by alaxfire

Not normal.
Blower motor - 05098030AA ( or leaves clogging it up )
or most likely the blower control module - 05096900AA.

( outside chance it could be the switch, but not likely )

best price is MB price for the control/resister module - try :
Car Part Wholesale - Auto Parts and Accessories Catalog - Blower Motor Resistor For 2003 Mercedes Benz SLK320 Base 6 Cyl 3.2L

for the blower motor :
Car Part Wholesale - Auto Parts and Accessories Catalog - Blower Motor For 2003 Mercedes Benz SLK320 Base 6 Cyl 3.2L

or you could get a used blower / module from car-part.com - many available