I imagine replacing O2 sensor and clearing CEL by resetting ECU will probably help a lot.

 

Tighten your throttle cable.

 

All it is a hiccup with your ECU.

 

It happens to a lot of S's so it doesn't seem to be a hiccup with the ECU since it cuts across the board with year models. Mine did it brand spanking new.

There is a lot of driveline lash on the S and I believe that is the cause. By that I mean the slop in the tolerances. Go under your car and twist the driveshaft. Mine has more play than any car I can remember.

I have found that my driving technique may aggravate or at least begin the situation. THe only solution for ending it is to get off the gas &/or release the clutch.

It goes back to throttle modulation. If I accidentally give it a tad too much throttle at low speed situations, like accelerating in the alley after backing out of the garage, and then back off quickly it begins. I do this at least once a week.

 

You can induce this behavior easily, like Wildncrazy said, by rapidly changing throttle position in 1st at low speed.

Hold the car at, say 15 mph, push the throttle in, and then let it back up, and push it in again, you'll get a nice oscillating bucking motion going on that won't go away till you really brace yourself and hold the throttle steady or clutch in.