Hoping to get some help with a recent issue with our car. We have never had any issues with car before. Maintenance and oil changes are current. Very low mileage less than 20K. As of Saturday morning there is a thump-thump-thump feeling under the gas pedal. You feel it under the pedal and sometime lightly felt on the floor on the passenger side. It REALLY feels like the beginning of a flat tire. We even pulled over to check the tires, twice, but the tires are fine. It is not a sound. Its a feeling. It's the most pronounced when foot is on the pedal, but not pushing down on the pedal. Saturday morning it was very strong and prounounced but Sunday, not so much. Almost thought it was all in our heads, until Monday morning and it was back again. What could this be? (I recall something similar happening to our old 2003 Accord. I believe it happened right after installing brakes on the old car and we were told it was 'brake dust'. But no brake installation with this new car. In fact it just happened out of the blue). Any suggestions?? HELP!