ipod mini reboot loop

I have just upgraded my iPod mini (2nd gen) with a 64 gigabyte CF card. I had iTunes restore the ipod, then synced my music with it. When it was done syncing, I told it to eject. It ejected, then came right back up with the folder icon and the "www.apple.com/support/ipod" link. I have tried to format the card with disk utility, but cannot due to a reboot loop. Whenever the iPod is connected to my computer (iMac running Sierra OS with latest iTunes) it reboots every 5 seconds. It gets through the apple logo, shows the folder for a sec, then switches to the "syncing, do not disconnect" screen. It then powers down, and repeats the process. I am connecting it to a USB 2.0 port on the back through a wire that I tested with my brother's iPod (also a mini, same gen, just 16GB card instead).What should I try now?

I can answer any other questions you have regarding the setup I'm using if more info is needed.

Thank you in advance for any advice on this.