I have had  an XPS 18 for a couple weeks--not exactly a laptop, I know. It seems to brighten and dim "random.' If it just sitting on its stand with whatever open it brightens and then a while later darkens. It just goes back and forth. Sometimes a couple times a minute and sometimes less noticeably.

Not sure that a Windows 8/8.1 glitch a Dell glitch or just a defect in my machine.

Any similar experience or advice?

Thanks