vibration under the car
Does it seem to occur in the 30-40 mph range, as you accelerate? Maybe feels like you are running over a rumble strip? You have an automatic transmission, right? Then, torque converter lock-mode problem should be considered. Pretty common topic here, you can see what others have said by searching past posts for “torque converter shudder”, forum search link, upper right this page.
you should still be under warranty. bring it to the dealer.