A problem with my xps 17 laptopscreen

I have a question. I have just bought an xps 17 laptop with an nvidia GeForce GT 550M. I notice that when I leave the computer alone for a while, he gets a black screen (which is normal) but when I move my mouse to get my screen back, then I get an unnatural bright screen. Is this normal or how can I solve this problem? I already went to the nvidia site to look if there is a new update but there wasn't.