There are many things you can try. Try the latest beta version 4.2.7 from the homepage and see if it also causes slow logon when 'Start automatically for this user' is enabled.
Also, does manually starting it from C:\Program Files\Classic Shell\ClassicStartMenu.exe also cause a slowdown? In that case, capture a slowdown dump as per the instructions here:
viewtopic.php?f=12&t=6If the startup/logon delay is only due to the 'Start automatically...' setting and it causes no delay when started manually, let's troubleshoot it further. Make sure no other Start Menu replacements are installed along with Classic Shell. Turn on 'Start automatically for this user' and follow these steps:
1. Open Regedit and go to HKCU\Software\IvoSoft\ClassicStartMenu\Settings
2. Create a new DWORD value named LogStartup and change its value to 1.
3. Restart Windows and log in.
4. Go to the folder %LOCALAPPDATA%\ClassicShell and look for a file named StartupLog.txt
5. Attach it here.
After the log is created, you can turn off 'Start automatically for this user' until it is fixed.
If the menu is loading without any delay when started manually, as a temporary workaround, you can create a shortcut to C:\Program Files\Classic Shell\ClassicStartMenu.exe and paste it in your Startup folder at C:\Users\<your user name>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.