Chosen Solution

It’s charged 100% and turns on but instead of playing a song, there is a repetitive ticking sound. Sort of like a clock tick. Nothing plays.

Is the ticking audible without headphones? If so, the hard drive will need to be replaced. iPod Classic Hard Drive Replacement

Try backing up your iPod to your computer and restoring your iPod to its factory settings. Load some of your songs back onto your iPod and see if this continues. https://support.apple.com/en-us/HT201252 https://support.apple.com/en-us/HT203977