Unstable engine running at idle 750 RPM

My Aveo is 2010. with 1,2l 62KW.
At 60000km reached engine started to work unstable at idle 750RPM.
I feel little bit on steering wheel and inside car that engine is shaking. Looking to engine how works, easily could see that every 5-10 seconds engine loose some RPM then fast increase not to shut down - it is seen on tahometer too...

When engine is cold and idle is 1000RPM until warm up, there is no engine shaking. Also, when is 750RPM and turned on air condition, engine stop shaking and run smooth.

I guess that on minimum power needed to produce on 750 RPM some regulation valves or flaps for air and fuel not running good...

Does anyone can help and tell which part has to be replaced?!