Not a classic O2 sensor symptom - sounds more like ignition. A friend has similar symptoms and it turned out to be a fried distributor rotor. Make sure your cap, rotor, wires + plugs are all in good shape.

The other thing this sounds like is a failed catalytic converter, when the innards break loose and clog the outlet. You hit a bump in the road and the shock dislodges the blockage - but it happens again and again. With the engine off and the exhaust system cold, get under the car, grab the pipe just aft of the cat, and give it a good shake. If you hear stuff rattle inside the cat, there's an excellent chance that's your problem.
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Thank goodness we don't get all the government we pay for. -- Wiley Post