Possibly Electrical?

I have a 1994 Grand Prix GTP, with some problems. When I start it up in the morning and take off, about 3 miles down the road it will overheat. I typically just shut the car off and I then turn it back on and the gauges goes back to where it is suppose to and stay that way for the rest of the time im driving it until i let it sit and start it again, Im not sure whether or not the car is actually overheating but i don't know alot about cars and I don't wanna take it to a shop til i have some info. I did talk to someone who said it could be my ECM that is failing which is causing my gauges to go wacko, for example when im going 60 it will say im going 80 but the needle jumps or my blinkers only stay on instead of blinking but it doesnt always do that. I am mainly worried about the overheating, if anyone can help me out I would appreciate it.