On virtual machines without internet access it may take 1-2 minutes to start SharePoint Management Shell. The problem is that when loading signed assemblies the .NET Framework checks the Internet based certificate revocation list. The timeout for each check is 30 seconds. To avoid this check, set the following registry key:

[HKEY_USERS\<userid>\Software\Microsoft\Windows\CurrentVersion\WinTrust\Trust Providers\Software Publishing]
"State"=dword:00023e00