My JBL 6disc CD changer in my 04 Camry was the same. It felt pretty warm like a toast out of the toaster. As long as it doesn't feel uncomfortable to grab, you should be okay.

 

That's normal. They're spinning at a very fast RPM over rollers and such, and being encased in something that gets warm anyways.

 

Discs are not hot or warm when I eject them immediately after playing in my JBL multi-disc stock head unit (05 LE). The problem I have with my player is CR-R discs skip, sometimes badly, after playing them for 10 or 15 minutes even though they play fine in other CD players (both home and auto).

 

Chances are your heater vents run right above or below the CD player. Are you running your heater through the dash vents?

 

The excess heat is most likely being generated by the amplifier in the head unit. Warm CD's are normal if played for any amount of time.

 

Toyota has a microchip which detects the mood of the music in the CD and appropriately heats up the CD in case the music's hot.

 

That is absolutely correct.