You can stop, start and restart some of Plesk services directly from the control panel.
The services available for restart are:
In order to stop, start or restart a certain system service follow these steps:
Click on the Restart Services button on the Server administration page. The Plesk services restart page appears.
To start a service: click on the icon
(Start service).To stop a service: click on the icon
(Stop service).To restart a service: click on the icon
(Restart service).
The current service state will be marked by an icon: 
(On) for the service running, 
(Off) for the service stopped, and 
if the given service is not installed or its management capabilities are not supported by the license key.