01 deville idle

I have a 01 deville. The idle started to act up. It changes up and down when car is started up. And sometimes when i stop for a lite... Any help???? Thank you.

Many things can cause this, bad o2 sensor, vacuum leaks, idle air control carboned up, sticking egr valve, start with a full scan and check for pending codes.

i found out car has a bad trans mount, the one front near front bumper, thanks