My gamecube won't stay on. when i turn it on it will go off in about 3 seconds or so.

anyone know what might be wrong?

Maybe a dog is tripping over the wire. :haha:
Just kidding. Make sure the outlet you're using isn't faulty i.e. plug it into an entire different outlet on a different current to make sure thats not the problem.
If the problem still persists, check if the cable is plugged correctly into the GC.

Have you used the Gamecube before? Or did you just buy it from a store?
Also, make sure the game is compatible i.e. PAL is for European games, while NTSC is for American games. Check the box if all else fails.

I hope everything works out!

i have had the gc for several years. it just started doing this the other day.

Did you try the suggestions I posted?