Car shaking at Idle

let me just start off by thanking all the guys that have helped me with previous problems...lol i feel like i write something on this forum every couple of month...

ok here is another problem
the car start of very nice...once reaching operating temperature which is the middle or a little bit above the middle cause the aleros like it like that.
i feel a vibration though the steering wheel and the shifter..this happens only at idle while stoped at a red light or stop sign..while its moving it rides like a charm..the idle needle moves in small incriments so i cant realy say its a rough idle..i have changed the plugs and wires with some realy good oness...i cleaned out the throtle body and the MAF sensor.
my next step is going to be changing the transmision fluid and getting a new O2 sensor...before i do any of that i was just wondering if u guys have any idea of what it can be causing that. some one told me it can be a EGR sensor.

it has 75000 miles and its a 2001 3.4 alero