My 96 mercury sable shakes like crazy in mornings and turns off?

In the mornings the car shakes uncontrolably and engine light blinks on and off it also turns off. It only does this early morning. My car shakes alot when engine is cold nd engine light flashed on and off once it warmed up it got power back spark plugs were just cha.ged I read it with a scanner and it said coil A & B weree failing also changed plugs because they were misfiring, when I accelerate car it makes a crackling noise weird like rattle or electric