hold down home button and sleep button until it shuts off and then try it. that's called a soft reset. if it keeps messing you plug your iPod into your computer with iTunes and backup and restore. that almost always fixes problems
Try giving your iPod a forced shut off. This is achieved by pressing the on and off and home buttons simultaneously. If you press for too long, the iPod will reboot. When the screen of your iPod goes dark, let go off the buttons.