Here is the short version of the story. When you import the Active Directory PowerShell Modules (Import-module ActiveDirectory) it takes some time to load.

To speed things up run this command first:

$Env:ADPS_LoadDefaultDrive = 0

If you want to know more about it you can read the Blog post below.

Active Directory Powershell Blog - Disable loading the default drive ‘AD:’ during import-module