Windows 10 boot suddenly takes 10-20 minutes

The WinLogonInit phase is slow.

What Happens in This Subphase
The WinLogonInit subphase begins when SMSSInit completes and starts Winlogon.exe. During WinLogonInit, the user logon screen appears, the service control manager starts services, and Group Policy scripts run. WinLogonInit ends when the Explorer process starts.

Visual Cues WinLogonInit begins shortly before the logon screen appears. It ends just before the desktop appears for the first time.

WinLogonInit Performance Vulnerabilities Many operations occur in parallel during WinLogonInit. On many systems, this subphase is CPU bound and has large I/O demands. Good citizenship from the services that start in this phase is critical for optimized boot times. Services can declare dependencies or use load order groups to ensure that they start in a specific order. Windows processes load order groups in serial order. Service initialization delays in an early load order group block subsequent load order groups and can possibly block the boot process .

After applying the FullBoot.Boot.wpaprofile go to the Generic Events - Generic Fullboot table and expand the Microsoft-Windows-Winlogon provider, look for the tasks that belong together (same taskname but 1 Event with Start and 1 with Stop Opcode) and look at the time column and subtract the starttime from the endtime to get the entire duration. Now the task is very long.

In the sample, RequestCredentials (entering password) and AuthenticateUser (checking typed in data) takes too long.