PLEASE HELP 1ST TIME OWNER

I HAVE A 2005 HYUNDAI SONATA AND WHEN I GO OVER A BUMP IT FEELS LIKE THE BACK OF THE CAR GOES KIND OF SIDEWAYS ONE WAY OR THE OTHER DIDN'T THINK THAT IT WAS A BIG DEAL AND JUST HTIS WEEKEND I HAD PEOPLE IN THE BACK SEAT.THERE WAS SNOW ON THE GROUND AND IT FEELS LIKE THE BACK END WAS KIND OF FLOATING OVER SOME BUMPS IT DID NOT FEEL LIKE IT WAS SLIDING ON THE ICE.IT DID IT A COUPLE TIMES ON DRY PAVEMENT ALSO. IT FEELS LIKE A TIRE IS FLAT OR MAYBE THE TIRE HAS A BROKEN SIDEWALL.IS THERE SOME KIND OF TRACTION CONTROL ON THE BACK OR SOME SORT OF NEW SUSPENSION THAT I AM NOT USE TO.YOU CAN EMAIL ME AT mikecartmell@cox.net if you have any answers or suggestions for me.
 
 
Thanks'
Mike Cartmell

Have the dealer look at it.  I know someone who has an XG350 that had something replaced on the rear suspension because it broke.