noise when car is going down the road sounds like running over a rumble strip on 2003 Mercury Grand Marquis

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
the noise is very light you feel it more than anything and it is when you let off the gas sometimes or when you go back to accelerating feels like you are running over a rumble strip in road but just very lightly what could be the problem
(1) Answer