What's causing my CD-Player audio to randomly cut-off?

If the speakers actually gradually fade in and out try pulling all of the fuses for the radio for 15 minutes to reset it. OTOH if the speakers cut in and out suddenly and with a popping noise then you have a chafed wire or a terminal that is touching the grounded body of the car. On almost all car head units (factory and aftermarket) all 8 speaker leads float at slightly less than half of the battery voltage at all times so if any of the 8 touches a ground the amp chip in the head unit shuts down to protect itself.