Under Windows Server core, if you can’t control the services remotely, the commands to change the services are as follows:
sc config <service_name> start= <mode>
auto = automatically started at boot time (automatic)
demand = manually start the service (manual)
disabled = Service can’t be started (disabled)
Start and stop services using:
net stop mssqlserver (default instance)
net stop sqlserveragent (SQL Server agent default instance)
net start mssql$sql2014 (SQL Server instance called SQL2014)
net start sqlagent$sql2014 (SQL Server agent on instance called SQL2014)