A moody 97 grand am

HELP I Am soo sick of my car.
My car has about 115000 miles on it. I have had the fuel injectors all replaced and a new water pump put in. But Every once in a while the car will shake when I am idling. But when I am driving it is fine. But after I drive it about 30-40 miles it stops doing that and the check engine light goes off. I went to the macanic and he doesnt see anying and does'nt do anything and the car stops shaking and is fine. So I Am at a loss. what could be the problum.

if im not mistaken it could be your egr valve i now someone that was having simular problems and had it scanned and it was egr valve. Autozone does the scans for free. Hope this helps.

timing?
I hate autozone but you can rent the obi wan kanobi II and use it yourself.
Worked there 10 years (2 years with Chief auto)the originator of Autozone is rolling over in his grave with what they did to that comp.