Good Morning everyone!
I've been looking at a 2012 mercedes c250 coupe recently with 97k miles and overall its a good ride. While test driving, i realized that none of the radio buttons were working like the radio button, am/fm, nav, and the rest and same with the dial knob. What could be the issue for this?

@tashfin - Could be anything - bad fuse, water intrusion, corrosion, chewed wires from mice etc... first I would check the fuse panel that operates the radio. If that is good, I would pull the unit out and inspect for corrosion, water intrusion, chewed wires from mice.. and go from there.