The iPod "Classic" is the current gen....it's the more improved version of the 5th gen with video. My grandpa's (yes he has one, though it's a 5th gen) was doing the same thing.....and still does occasionally. They've been about for around 2 years, so if you bought it less than a year ago, then you can get it replaced fairly hassle-free. If you bought it sooner than that, it will live for a while longer....and the problem may resolve itself (because of it moving when in your pocket or something). His has been fine while doing that for about 6 months, so I kind of have proof. Mine is a classic, and has yet to do that, so your situation is slightly unique in that sense, though there isn't much difference between the generation but drive size and software (small difference).
HOWEVER: If you are seeing that it is freezing/hanging before getting to a song, then it may be close to death. If that's happening, seek the warranty out NOW.
Hope my info helps you in some way.