Like anything electronic, iPods can do weird things. They can freeze up and not play any music amongst a long list of other things. If you iPod is not broken, a restart will usually fix the issue and you can go back to listening to your favorite music or audio books.
How to do it?
Restarting your iPod is a lot easier than you think. Simply take two fingers and simultaneously hold down the 'Menu' button and the 'OK' button. After a few seconds, the screen will go dim and the 'Apple' logo will show up on the screen.
Give the iPod a minute to restart, then if things were acting up, they should be back to normal!