What could be the problem with my 2003 Buick LeSabre Limited?

My car runs fine for the most part, just had the
coils, plugs & wires, fluids, and fuel filter all
replaced. But here recently but not every time it's
driven all of a sudden the check engine light
comes on the car will idle up past 3 and jerk my
whole car and when stopped it'll idle down
between 0 & 1 and I'll have to press the gas pedal
to the floor for it to go and it'll jerk and idle back up
high to take off, and I'll have to pump the gas pedal
to keep it at the speed limit or it will idle down. I've
almost gotten hit twice because of this and I can't
figure out what is wrong with my car. It's done this
3x in 2 weeks.