Why is the resolution so low when I start my laptop?

I will or must use my laptop on a monitor. However, I have a problem. When I switch on my laptop the resolution is only 1280x720, but when I restart it the resolution is at 1920x1080.

At some point it gets really annoying… It really can't be on the monitor.

Do you know what I can do about it?

Graphics card: AMD Radeon HD 6480G

You have to set this in the driver.