Enable sysadmin user to restart SQL server from management studio
If you connect to SQL Server from a Machine M which has SSMS installed but your account is not local admin on Machine M you would find the option of start/stop to be disabled or greyed out. OTOH if you are local admin on the Machine M you would find the option to be enabled. When you do this from server on which SQL Server is installed, you are administrator there and hence you see the option. It does not matter whether your account is admin in SQL Server or not when you connect from machine where you do not have local admin privileges you would see the option disabled, however you would still be able to perform all sysadmin activities in SQL Server. This is not a complete statement their could be other reasons as well, this is what mostly I have observed, please check and let me know. Please also refer to SQL Server agent start stop and restart disabled blog to know more about reasons why this could happen