Ipod 5th gen not recognized on computer...

Hey guys/gals...

I need some help. I have a 5th gen Ipod that I can get it into disk mode to try to restore it but it doesn't appear on my computer. I've tried both mac and pc machines with no luck. After like 30 secs of it being connected to the computer it'll power off and go back to the sad face but before the sad face for like a millisecond i can see the ipod under my devices.

Any help in where I can restore my ipod?

Thanks.