Why Car makes intermittent shuddering sound which goes away when I step on brake

Took car today to Midas for brake checkup and test drive.Manager took test drive and heard the sound and how it went away upon stepping on brake.Midas technician will look at right brakes tomorrow as he says there is a high probability it is the brake pads and/or warped rotor.Thanks for the excellent advice.Will know better after the brake repairs have been completed and car goes on another test drive.Midas changed brake pads and rotors and so far intermittent shuddering sound has not returned on test drive..Only the next workweek of driving will tell for sure.Thank you.

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