Sometimes, you need to temporarily start a service (such as SSH) to perform some maintenance task. PowerCLI can help you with this:

To start the SSH server on each host of a vCenter:

Get-VMHost | Get-VMHostService | ? {$_.Key -eq "TSM-SSH"} | Start-VMHostService

To stop the SSH server:

Get-VMHost | Get-VMHostService | ? {$_.Key -eq "TSM-SSH"} | Stop-VMHostService -Confirm:$false

As always, you can make adjustments to the oneliner to select another service to start/stop, or further limit the selection of hosts to a cluster or a group of hosts (e.g. filtered by name).