I had a similar problem years ago with an Oldsmobile. Turned out to be the crankshaft sensor was going bad. Took several trips to the dealer before it finally failed while in their possession. My car would misbehave once it had run for awhile , eventually bucking and acting liking the timing had gone out. Because it had! The car's timing was driven off of the signal from that sensor. Once the car sat for twenty minutes or so, it would drive normally again, at least for time. Seems that the sensor was mounted opposite the rotating crankshaft pulley. Overtime, since the sensor was mounted too close, it would actually abraid and heat up and fail.
Not saying this is your problem exactly but this is an example of how these types of symptoms sometimes are just a small sensor issues.