This article explains how to reset an iPod Touch from generations 1 through 7, released up to and including 2019.
iPod Touch 5th Gen A1421 Reboot with Buttons – Forced Reboot – Hard Reset
If your iPod Touch continues to experience app crashes, freezes, or other issues, follow these steps to restart the device:
Press the Sleep/Wake button (located in the upper corner of the iPod) until a slider appears on the screen. It says Slide to Power Off (the exact words may vary in different versions of iOS).
Release the sleep/wake button and move the slider from left to right.