Just noticed it in the last week on my 212,000 mile Insight. On the first start of the morning, it feels rough and the engine is shaking like it might be running on 2 cylinders. After about 20 seconds it smooths out. Runs great at other times. Has the correct Honda plugs which were in good shape when I check them 1,000 miles ago. What can I check for if the problem only lasts 20 seconds when cold?