Crazy engine light

1994 Buick Park Av Ultra 156,000 miles 3.8 supercharged

As soon as I start the car it is fine thenabout a mile the check engine light comes on and it runs rough, now if I pull over and shut off the car and restart it goes off, it runs for about 1-7 miles doun the road then it comes on, runs rough --and same thing. Pulll over etc. Now if I dont pull over to shut it off, and keep it running rough it stalls and dies, I tried this, I pulled over with the check engine light on and kept it running at idle it ran like crap after a few minutes, I pressedthe gas and it went back to normal. Heeep me, thanks