First login screen disappears!

The first login screen disappears and i have to enter the password blindly to go on …

I am not at all sure what you are referring to. Could you share a picture/screenshot of what you are seeing?

I can’t!
It’s really simple. When i first boot up, the login screen appears for just a second and then completely disappears (blank screen). Then i have to enter my password blindly on the blank screen to gain access to my plasma desktop.