but then I connected it to a wall charger, and it began charging like normal.
Might be something here > Powering Apple and third party peripherals through USB
Did you try a different USB port?
Thanks for responding, Carolyn.
I don't think this is a problem with peripherals. That wall charger I referred to is an Apple product; when the iPod is connected to the wall charger, it charges perfectly fine. It's just the Macbook that randomly stopped recognizing it. Very bizarre and frustrating.
That SMC link you provided was broken, unfortunately. What does resetting the SMC do?