but it isn't a "full" reboot. It only takes four or five seconds instead of the usual 12--14 seconds since it skips the intial waving penguin logo

When it does that kind of reboot, what's happening is that the player binary is crashing and exiting to the shell. Then the init script restarts the player binary automatically.

This usually (but not always) indicates some kind of minor bug in the player software which isn't bad enough to have trashed the kernel. Tux doesn't wave because he's in the kernel.