If you leave your iPod shuffle or iPod nano connected to your computer when you restart or start up a Windows-compatible PC, you might encounter up to a 3-minute delay on startup. You can either wait it out (if you don't mind waiting), or disconnect your iPod shuffle or iPod nano and wait until the computer has started before reconnecting it.
For more information on this situation and how to permanently avoid it, read this article.
On certain older Power Macintosh G4 desktop computers, your computer may boot into Open Firmware if your iPod nano is connected on startup. To avoid this, use a hub to connect iPod nano to your computer, or wait until your computer has started up before connecting your iPod nano.