Q: Ipod classic, 120gb randomly freezes and/or reboots. Is this hardware or software issue?

My wife told me the other day that she was having an issue with her ipod which was happening at an increasing rate. While listening to an audio book or music it will randomly stop/freeze, and times the Ipod will reboot. Of course, when listening to a 6 hour audio book and losing your place when this happens can be frustrating. It's about 4 years old and I was thinking that maybe it was the drive inside, but not sure.

Thanks in advance,

Brian