Just b/c you just bought it does not mean the alignment/balance is on point. I would take the car back to the dealer, demand a free alignment/balance, and make sure everything is checked out and on point. It could be as simple as your wheels need balancing.
When buying a used you should always make them change the air filter, do an oil change, check the tires (change if necessary to new), get some new brake pads, and any other needed maintenance. Those things are fairly cheap for a dealer and they will usually throw them in.