SQL Server Agent jobs can be set to start automatically when SQL Server Agent starts.
To find all jobs set to run automatically when SQL Server Agent starts, use this query:
SELECT j.name AS 'Job Name'
FROM msdb.dbo.sysjobs j
JOIN msdb.dbo.sysjobschedules js ON js.job_id = j.job_id
JOIN msdb.dbo.sysschedules s ON s.schedule_id = js.schedule_id
WHERE s.freq_type = 64;
To see how to Schedule a Job to Start Automatically when SQL Server Agent starts, read related Article:
Schedule a Job to Start Automatically when SQL Server Agent starts