When traveling on the highway and u loose power?

The loss of power came@ about 70mph and I could keep it @ 50-55mph till I pulled off. I then turned back home and got to the next exit before I shut it down and waited about 3 minutes. Fired it back up and didn't have a problem since, but the check engine light goes off from time to time. Any insight would be great. The car is a 2000 Grand Am SE1 w/ a 3.4L V-6 automatic.