any idea where to start looking for the cause of this?

Basically it's just started about 2-3 months ago. When i start the car i get a vibration almost like a shudder around 1,000 rpm when the car idols. Give it gas and it goes away. It's not bad, but it never happened before. It's not a constant vibration, it oscillates every couple of seconds.

The best way i can describe it is if one of the pulley's is slightly loose and has a little vibration as it spins. That's probably the first place i will check. Second place i will check is a belt to see if it's cracked or if there is a problem.

Thought i would ask if anyone has experienced this before?

sounds like a slight miss. id check the plugs, and also run a can of seafoam in the gastank to make sure the injectors are clean. any engine codes?

Check your trans mount also. Mine was idling smooth until I got up to 1000 RPM and above and then the quick vibration came through the car. I replaced the mount and it was split in half, now the vibration is gone. Just have a vibration in gear at idle even after I neutralized the transmount but I think it is because of a faulty TP sensor or air bypass valve.

thanks for the replies.

No engine codes.

I will check the plug wires to make sure they are secure.

A little more information, it's not a really bad shudder, it's just enough for me to feel through the seat and steering wheel. Doesn't make any strange noises.

sounds like the clutch for the fan is locked up . If its making alot more noise like a turbine when revved when the car is still cold , that's the problem.