Please make sure you have the latest version of the System Software installed by selecting Settings > System Software Update. The system will then restart.
If you cannot reach Settings, please update the System Software using Safe Mode option 3.
If the error occurs again, back up your saved data and initialise the PS4 system by going to Settings > Initialisation > Initialise PS4 or by using Safe Mode option 6.
If the error continues, please contact PlayStation Support.