Manage SQL Server Services from the Command Line

To manage the default database server instance, use these commands:

NET START MSSQLSERVER Starts SQL Server as a service.

NET STOP MSSQLSERVER Stops SQL Server when running as a service.

To manage named instances of SQL Server, use the following commands:

NET START MSSQL$instancename Starts SQL Server as a service, where instancename is the actual name of the database server instance.

NET STOP MSSQL$instancename Stops SQL Server when running as a service, where instancename is the actual name of the database server instance.

Read more at https://technet.microsoft.com/en-us/library/dd421654.aspx