If this were my problem, I would first do a basic health check on cpu/memory/disk. Then a deeper dive into the disk performance of the C drive. Verify that it's responding ok and that I/O requests are not being queued.
Then I would run Process Monitor to see what I/O Powershell is doing.
https://learn.microsoft.com/en-us/sysinternals/downloads/procmon
In the Filter menu option, set an "include process name is powershell.exe". Then open a PS prompt and run the command. Stop the trace and from the Tools menu review the various Summary reports to try to figure out what is taking the most time.
You might have to run that same analysis on a "good" server to see if you can find a difference somewhere.