Bouncing in my seat

because my track frame's so compact (short in length but high in height) i find when i hit a bump/crater in the road, my rear wheel bumps up and down and I end up bouncing around untill i get my rythm back and the frame settles down.
this sound like what your talking about?

that actually happen to me a fuckload of them when I cycle down the Kingsway road near Holborn, the road are a piece of shit there.