Recently did you set any sql perf alert?
If so that count didn't pass the threads you set. Ideally the way SQLAgent figures out if there are any thresholds changed for the alerting system.
If you 're well versed about setting SYSTEM REGISTRY settings then you can change the sampling interval in registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\servername\SQLServerAgent key, PerformanceSamplingInterval - default is 20 seconds.
But before that make sure backing up of your registry.