Remove CCleaner In System Tray When Computer Starts

CCleaner now showing up in the notifications area (system tray) after rebooting v 4.18.4844

You have enabled active monitoring

To disable

Run CCleaner

Go to Options

Select monitoring 

Untick :  Enable Active Monitoring

Older versions you also have enable active monitoring in the advanced menu

If Enable active monitoring is not highlighted then untick Enable system monitoring first then untick  Enable active monitoring.