I have a 07 G35x and lately I've been having this issue of the car shuddering during low throttle. The RPM will bounce up and down during this time (couple hundred fluxuation). It only happens after a few minutes of driving when the car is warming up and for around 30 seconds. It then goes away and never happens when the car is fully warmed up.

The duration seems to change depending on the temperature outside and can be shorter or longer. It never lasts longer than one minute.

My transmission fluid was changed about a year ago with Matic S and the level looks good.

What do you guys think?

 

Clean throttle bodies maybe?

 

Does it seem to be an engine problem? My G had worn out driveline bushings which gave an odd feeling going on-off throttle that felt like lugging at low speeds.