A recurring buyer-beware item: a $20 plastic brake-light switch under the pedal can fail from age or a panic stop, dropping the car into limp mode and forcing very low speeds. Owners advise keeping a spare in the glovebox; the fix is a cheap 10-minute DIY for the suitably contorted.
Cheap brake-light switch that triggers limp mode
Mercedes-Benz SLK / SLC · buying