Sooty torques
Oooh, careful love.......
I get this on occasion, just put it down to driving a diesel and resonant frequencies etc. Doesn't happen all the time, but I do notice it more when the engine is cold.
Always have a look round to see if there's a Transit, bus, truck or any other diesel nearby for that matter. The low-frequency resonances and harmonic vibes can feel and sound quite alarming at times.