Car Engine shakes at start when it is cold.

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Hi, I have Nissan Altima GXE 1999 (140 K Mileage). When I start the car in the morning or after a long rest (3-4 hours), car engine shakes wildly for some 20-30 seconds before coming to normal. Now check engine light is on due to misfire of one of the cylinder it seems. I greatly appreciate your help in this regard. Thank You! Hari. This doesn't happen if I start after driving for some time. It behaves normally once I drive little bit or Temparature shows in working temparature(Needle in Middle).