My car just started making a vibrating noise recently, coming from the undercarriage. At times it sounds louder than at others. I tried listening from the underside of the vehicle, and the noise seems like its coming from underneath between where the front and rear seats sit. but I can’t tell if its louder on the driver or passenger side. The makes a continuous rattling or vibrating noise, but seems like it went away some when I was on the Interstate. It might get louder when I am stopped at a light.