Try double clicking the home button, and holding down on the apps that slide up from the bottom of the screen. Hold your finger down on one of the apps until a red minus sign appears, and keep clicking the minus signs until all of the apps are gone from the multitasking tray. This should free up some RAM and help your iPod stop crashing. Also restart the iPod every once and awhile to keep things fresh. The iPod 4 is running on some pretty old hardware and is already discontinued by Apple, so the device is going to be pretty slow and crash unfortunately. :( This should help though...