Every now and then (say, 15 mins or so) the title bar will blink (i.e go from blue to a lighter shade of blue), as though I had clicked somewhere outside the window. At that moment, for about a second, it will stop whatever I'm doing. If I'm watching a video in fullscreen, it will exit from fullscreen. If I'm typing on Word, the letters that I type in that one second pause won't register, and it will play that error message sound.
It's getting kind of annoying now, so wondering if anyone has any experience of this or could diagnose its cause?