The Windows 10 VDA exhibits slow logon during the launch. There will be 30 + seconds delay while loading the profile and the screen will be processing the "Welcome" Screen during that time. 
 

DelayedDesktopSwitchTimeout registry helped to fix the issue.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. 

1. Open the registry editor 
2. Locate the following registry subkey:
3. HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
4. Double-click the DelayedDesktopSwitchTimeout registry entry.
5. In the Value data box, type 5, and then click OK.
6. On the File menu, click Exit.

---

Problem Cause

During the Logon phase, there are several phases such as Session Creation, Authentication, LogonScript and Profile Loading... The delay is observed while the logon process calls the "LogonScript". During this phase, the Windows OS has to switch from Session 0 to the new Session (example, 1 or 2), thus there will be delay of 30 seconds observed.