2015 GMC SIERRA Unknown Or Other Problems

MY VEHICLE SHAKES AT HIGHWAY SPEED. I CAN FEEL IT IN THE STEERING WHEEL, AND SEAT. VISUALLY I CAN SEE THE BED OF THE TRUCK SHAKE. THE ISSUE HAS NOT GONE AWAY.

A WEEK LATER AFTER BUYING A NEW 2015 GMC SIERRA DELANI FROM ED MORSE GMC 'SAWGRASS I TOOK IT TO A TRUCK ACCESSORY COMPANY TO ORDER A NEW BED (TONNEAU) COVER. THEY TOOK THE ORDER AND TOOK A PICTURE OF THE SERVICE PARTS IDENTIFICATION LABEL, LOCATED IN THE TRUCK GLOVE BOX FOR THE PURPOSE OF ORDERING THE PART AND COLOR. THIS IS THE ONLY PLACE IN THE TRUCK THAT IDENTIFIES THE PARTS AND COLOR FOR THIS PARTICULAR VEHICLE. I AM ENCLOSING A PICTURE FOR YOUR REVIEW. TEN DAYS LATER THE COVER ARRIVED AND WHEN I WENT TO THE COMPANY TO HAVE IT INSTALLED, THEY REMOVED THE WRAPPING TO SHOW ME THE COVER AND WE FOUND OUT THAT IT WAS NOT THE RIGHT COLOR. THE COVER WAS WHITE INSTEAD OF BLACK. THE COMPANY MANAGER CHECKED THE ORDER TWICE TO VERIFY THAT THEY HAD ORDERED IT CORRECTLY AND THAT HAD THE CORRECT...