Вот готовая процедура для запуска Агента.
\nuse master
go

if exists (select * from sysobjects where id = object_id(N'[dbo].[sp_autostart_sqlagent]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)
drop procedure [dbo].[sp_autostart_sqlagent]
GO
SET QUOTED_IDENTIFIER OFF SET ANSI_NULLS ON
GO
create procedure sp_autostart_sqlagent
as
declare @retcode int
declare @local int

exec @retcode = sp_OACreate 'SQLDMO.SqlServer', @local OUT
if @retcode<>0
return -1

EXEC @retcode = sp_OAMethod @local, 'Connect', NULL, '(local)'
if @retcode<>0
return -1

declare @js int
EXEC @retcode = sp_OAMethod @local,'JobServer' , @js OUT
return -1

EXEC @retcode = sp_OAMethod @js,'Start'
if @retcode<>0
return -1

return 0
GO
SET QUOTED_IDENTIFIER OFF SET ANSI_NULLS ON
GO
exec master..sp_procoption 'sp_autostart_sqlagent','startup',true
go