If you bought a first generation iPod between September 2005 and December 2006, you can replace it for a new one! Apple support has recently found that the first iPod nano had a manufacturer defect that caused overheating. Keep in mind that not all of these original nanos are defective, but Apple service techs urge you to verify yours.
To find out if yours is eligible for replacement, you’ll need to verify your serial number with the Apple service replacement program. Just enter your serial number to see if you can replace it. If it’s not eligible, than it’s somewhat of a bummer. But, at least if it’s still working, you know your iPod nano is not defective and won’t overheat on you.
Look, this is a 6-7 year-old device, so if it’s eligible, then you’re a lucky stiff. If it’s not, then you should have already bought a new one by now! In regard to why the iPod nano first gen overheats, it is directly related to a single battery supplier who distributed a faulty battery which heats up the unit to much. This could cause a safety risk, such as burning, so you either want to replace it right away or not use it.