Our 2014 RT-S was delivered with a tire shimmy/shake at about 40-45 mph. I brought it back to the dealer and they removed the tires and wheels and replaced them with some from a floor model. Also the tire pressure was way off when delivered. Correcting the pressure and replacing the rims/tires fixed the problem.

Older 's may have worn suspension bits ( tie rod ends, bearings ) but bad tires and rims are probably the culprits.

Lew L