Maybe the dust shield is bent and rubbing on the rotor? The brakes always have a slight amount of drag to them (the pads are always gently touching the rotors); maybe something was stuck to the pad or something. If it went away and did not sound like the wheel was going to fall off I would not worry too much.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine