There are two distinct possibilities. Do you have the vibration aka death wobble? It appears at highway speeds. That is a manufacturing defect in some of these vehicles, thankfully not mine. Read hundreds of posts at various RAM forums. People have found different solutions. Or do you have a rough ride of some kind? That might be reality vs expectations, something you can fix looking at PSI, tires, shocks, air, etc.
My 3500 is smooth as glass on a good surface but I feel every jostle on a bumpy road. It's what I expect with leaf springs and 4000 pound payload capacity. It's a super comfortable cruiser but I take it slow on dirt roads or pothole lane. Everything improves when under load.