I have the 15" mid 2014 Macbook Pro. It has been my workhorse and never a problem, until now. This has started happening rather frequently. It Just goes back to the log-in screen all on its own. I've noticed that it seems to do it when I'm entering numbers. it fades o black and then the log in screen pops up and I have to put in my password then it goes right back to what I was doing. Right now, it's just super-annoying but is this maybe a harbinger of bad things to come?