SQL Server Agent jobs can be set to start automatically when SQL Server Agent starts.
To schedule a job to start automatically when SQL Server Agent starts, expand SQL Server Agent in SQL Server Management Studio Object Explorer, right click 'Jobs' and choose 'New Job'
Select 'Schedules' tab and click 'New...':
Give a name to the schedule, and choose 'Start Automatically when SQL Server Agent starts' option from the 'Schedule type' drop down list:
Click 'OK', and the schedule to start job automatically when SQL Server Agent starts is set:
To see how to list all jobs set to start automatically when SQL Server Agent starts, read related blog post:
List all Jobs set to Start Automatically when SQL Server Agent starts