In my opinion the easiest way to get a "foreach scenario" done in an Orchestrator Runbook is a PowerShell Script.
Get the x servers from a SCCM collection. This is the "input" for the PowerShell Script.
Set the delay time variable to "0" at the beginning of the script
Use a foreach loop in the script for all x servers and add 120 seconds each "loop" to the delay time variable
Reboot each server with the calculated delay (The HyperV cmdlet should support the input of a delay time)
https://video2.skills-academy.com/en-us/powershell/module/hyper-v/restart-vm?view=win10-ps
That is the approach I would try.
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Regards
Andreas Baumgarten