In the Strategy Health Center Console, under the System Checks panel, there is an icon to allow users to manually trigger all system checks:

"Refresh System Checks" will execute all system checks in each Health Center node (both Master Health Agent and Health Agent).
Additionally, there are two scenarios that will trigger a Refresh of all System Checks automatically without human intervention:
Note: In the Health Center Console, there is currently no indication that a "Refresh System Checks" operation is in progress. Therefore, the time to finish executing all system checks may vary depending on many factors such as number of enabled checks or number of machines in a Health Center system.