When restart Windows 10, all data lost

It could have been an update.

In File Explorer expand This PC and then C: select Users and see it there is a temp folder. If there is then you are signed in with a temp profiles and need to restart 4 times using Start > Power > Restart.

After the 4th start check again. to see if either you settings and files are back or you still have a temp folder. While there check to see if there is a folder with your sign-in name. If there is look in the Desktop folder for the files and any others in the default folders.

Important

Do not move these files to your current sign-in as they will get removed again. Copy them to another safe location.

Hi M]ke, this is happening much too often at the moment, you are logged into a temporary account . . .

Before you do anything or move any files around
Restart (not shut down) your PC 4 times, each time let your PC get to the Desktop before the next restart, this will fix this issue a lot of the time . ..

Otherwise:

Please open Windows File Explorer
Navigate to C:\Users
Do you see two user folders that look like yours?
Open those folders and check inside Pictures, Documents . . . etc. and see if your files are there

If your files are there:

Create a new user profile with Admin privileges
Log into the new user profile
Copy all your data from the old profile to the new profile (Documents Library, Pictures Library . . . etc.)

If you still have not found your files, look for a Windows.old folder on your C Drive, expand that to open the users folder contained inside - check there for your files, icons . . .etc.

If you do find your files . . . etc. there, copy them out as soon as possible as Windows will remove the Windows.old folder in time

NOTE VERY IMPORTANT: Do Not copy your files into the Temporary profile you are currently in, when the situation is corrected, your files will be deleted with the Temporary Profile and will not be recoverable !!