1. Install New Firmware
Sadly, lots of otherwise good MP3 players are let down by the quality of their proprietary firmware. Apple's iPod is by no means the worst offender, but there is one huge drawback that most people loathe: iTunes (if you're on Windows) or Apple Music/Finder (if you're a macOS user).
2. Replace the Battery
One of the biggest problems with MP3 players is battery health over the life of the device. If you're an avid user, you can't reasonably expect your battery to perform well beyond three years, particularly on older models. Perhaps poor battery life is the reason your old iPod ended up in a drawer in the first place?
3. Use Your iPod as a Portable Hard Drive
Even if you've already got a newer iPod or iPhone, you can still put your old one to good use. Just like how you can use your iPhone as a USB drive, you can also transform your old iPod into a storage drive. This is an especially good idea if your screen is broken but you don't want to pay for a replacement.
4. Replace the Hard Drive
Hard drives will die eventually. This was a serious problem back in the early days of iPods, with the third generation version especially afflicted. But like the battery, if you've got the inclination, you can replace it yourself.
5. In-Car Music
While you can use your smartphone to play music in your car, you might want to avoid this. It's too easy to damage your device by spilling a drink or having it tossed during a sudden stop.
With your primary device safely in your pocket, why not use your world-weary old iPod instead? They have storage capacities that often dwarf those on modern smartphones, and utilizing one keeps you from eating up battery life on your main device.
Load the old iPod up with the music you want, and it can stay in the car for months at a time---you'll never have to remember to take it with you when your leave the house. You can charge it via your vehicle's USB port (or the cigarette lighter on older cars) and play it either via the USB or a standard AUX port.