This is likely due to the Auto Power Off timer on the unit. The default setting for units sold in the UK and EU markets is 20 minutes. All other regions default the power off timer to Disabled.

Recent EU and UK power regulations mandate that all products offer an automatic power off feature after a set period of inactivity. Leaving the CD player Paused or Stopped will start this timer.

To adjust this, simply go to the Setup menu by pressing the MENU key on the remote control and change the timer or set it to Disabled.