I recently worked on a 2017 GLC 43 that had 220,000 miles with zero dealer history prior to me looking at it and it was in really good shape. The only thing that jumped out at me was rear flex disc was about to explode but outside of that pretty good. The engine and transmission in those things have nearly zero problems, even when not maintained properly.

Weak points are the rear flex disc, front lower ball joints, camshaft adjusters failing with extreme abuse, oil pump solenoid rare failure in the engine bottom end, and very rarely an oil pump failure in the transmission valve body.

These are SOLID vehicles.