How big are your images, mine are 2 cpu, and that causes the cpu to be pegged during logon which freezes things. Once that calms down the start menu seems to be responsive. I'm still mainly on windows 7 though as windows 10 performance is still pretty bad compared to windows 7.
Our VMs start at 4CPU with 8GB Ram going up to 4CPU with 12GB Ram.
Don't know if might help...
I had to use this key for Windows 10 - 1709 or the start menu was working weird (blank icons,etc.) :
reg add "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ImmersiveShell\StateStore" /v ResetCache /d 1 /t REG_DWORD /f
Found out that key when searching start-menu problems, but it didn't anything on our new 1809 golden image.
reg DELETE "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v StartMenuInit /f