Every morning when I start my car, it gives rattling & shaking noise at the exhaust for about 20 seconds. Whilst the Rpm needle is also shaking a little up & a little down. The exhaust blows air (not visible smoke) like a hiccup for that 20 seconds. After that, the Rpm needle & exhaust sounds turn to normal & stabilize.

Dear all sifus, what is the real problem? Can someone clarify?
(Car is Altis 1zz Fe).

Thank you Quazacolt.