Hold the button up longer than you think you need to–20 or 30 seconds. That should shut it off. Turn it on again and see what happens.
Since it’s new, you could also just exchange it. It’s not supposed to behave like that out of the box.
The other possibility is that you put on some files it really, really didn’t like–did you put on anything from shady sources? Anything with a lot of unusual or foreign characters in the filename or ID3 tags? Because those will trip it up, but it would have to be pretty severe.