little shake when starting

[kp2bh]

I own a 2001 explorer 4.0 engine and in the morning when i started is a litle shake like when is missing but after warm up all ok.not missing whe drive regularly just some times when is idling and in the mornings. what to check?
thanks... jimmy

 

[robertoa1a]

How tuned up is it (regular maintenance, ie plugs filters, PCV, etc...)?