2002 Mitsubishi Galant stumbles and rough

When I first start the car it runs good but then like 2 mins later it stumbles runs roughs like if its missing bad then it do that for like 20 sec then clears up it do that every morning or if I let the car sit for more than 20 minutes I clean the throttle body new plugs and wires twice put on a idle air control vale and tps sensor still doing the same thing what could it be