Laptop screen is black but works with external monitor

[EladAssia]

Hello, sometimes when I turn on my computer it boots as if there an external monitor connected (but there isn't) and the display is on the laptop monitor is black. However, when I connect it to an external monitor I can switch it back to the laptop monitor and it works. I'd appreciate any advice.

 

[Saga Lout]

If you have Function keys to switch between internal and external, are those keys sticking?

 

[EladAssia]

There is one function key for that but I don't think it is a sticky key. When I try to press it, it doesn't change the monitor...