Not unless it gets really hot. It is normal for your iPod to get warm to the touch, particularly when it is being recharged.
Because of this, Apple recommends that you always remove your iPod from any case while it is being charged.
If your iPod gets very hot while recharging from the FireWire port on your computer, be sure that you are unmounting (ejecting) your iPod while recharging. You can do this on a Mac from within iTunes or Finder.
If you do not do this, the iPod’s HDD will spin constantly while attached to your computer’s FireWire port, causing the excessive heat. Updated: 09|09|02.