Hello water4soul,
Thank you for contributing to the Apple Support Communities.
It sounds like your iPod nano (5th generation) restarts unexpectedly when you press the center button.
Try restoring the iPod to factory settings using the steps in Use iTunes to restore your iPhone, iPad, or iPod to factory settings.
If the same thing happens after restoring, or the iPod can't be restored, it may need service. See the iPod Service Answer Center for help with the process and more information on topics like warranty and service pricing, battery replacement, and express replacement service.
Best Regards.