Unstable rbm on Cold Start

[drmagieed]

Three days ago when I start my aveo 2009 LS Sedan the rbm after 30 seconds be 800 and after a while it goes to 300 then 1300 and back again to 800. This happened for 2 min until it stable on 800. This also not happened every cold start from three cold starts happened twice. I forgot when the rbm goes to 300 the engine seems to be stopped but it rises immediately to 1300.
Thanks

[drmagieed]

I forgot to tell you the MIL is off. There are nor errors.
thanks

[drmagieed]

I will change the question:
Is this may be due to throttle body? Is it need cleaning? If so, What are the proper procedure for throttle body cleaning?
Thanks.