Rough engine idle and Check Engine light!

I am starting to think this truck should be yellow and ooze pulp! The last two days it has ran really, really rough when first staring it up. It felt like an unbalanced driveshaft , but I was in park! The "Check Engine" light was on but went off after about 3 miles of driving. This happened both days as I was just driving into town. Then shakey roughness of the engine went away also. A mechanic told me it might be miss-firing and to check the plugs, any other suggestions?

:x :x :x :x :x :x

Thanks, Tim