When I logged in my user the screen becomes black for a second and later it shows the desktop, this was not happening before it was selecting in monitor preferences "set as primary".
Before I selected "set as primary" in xorg.0.log appeared this:
[ 30.822] (II) intel(0): Modeline "1366x768"x0.0 76.32 1366 1414 1446 1610 768 771 776 790 -hsync -vsync (47.4 kHz eP)
Now with this:
[ 59.765] intel(0): switch to mode [email protected] on eDP1 using pipe 0, position (0, 0), rotation normal, reflection none
Also I never use a external monitor on my laptop.
I hope you understand 
