My 6th gen ipod nano will not switch off, so when I want to use it the battery is always drained. It does charge just fine though. How can I switch it off?

My 6 th generation ipod nano (brand new this summer) has suddenly lost the abitily to turn off. When I press and hold the wake/on/off button the rotating clock dashes appear as if it is turning off but then the screen goes black early and it then never switches off properly. This means it is constantly on. It charges just fine. Connects to my PC just fine. I've tried restoring via computer & resetting the unit itself, but nothing works. It means the battery never lasts when I want to use it, or when I go to use it a day or so later it won't switch on at all because the battery is flat.

Has anyone else come across this before? How did you solve it. Or should I just return it to Apple?