Honda Civic 9th Gen. Vibration at Idle?

Hi Guys,

I am a proud owner of Honda Civic 2013 (9th Gen) LX 4 door Automatic.
I bought it used for 52 Thousand KM and now it has 72 Thousand KM (20000 in a year)
As a rule I leave the car to warm up in cold mornings, however I started noticing something weird.

In the middle of warming up, The car starts to vibrate the RPM drops whil vibrating, the kind of vibration that would appear just before it stalls.
The car vibrates just for a second or 2 and stops, RPM goes up again and continous to warm up.

I used to feel the same vibration when changing gears (from Drive to Park or Reverse to Park) or turning on the AC, but was very mild, however still can be felt.

Otherwise, when the car is warmed up, it is idling perfectly.

I have already cleaned the throttle body not to long ago, and cleaned the spark plugs as well.
I have took it the dealer ship to advise on the issue, and ofcourse they didnt know what was the issue and decided it was normal!

Any assistance on this regard we be great.

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