So about a month ago, I went to open my sleeping MacBook and discovered it had shut itself down. I thought that was weird but forgot about it. The past week or so it's been doing it a lot more frequently. It's not every time and I don't know what causes it and can't reproduce it. The first time it happened, I don't think it was plugged in, but every time since then it has been plugged in. Any ideas what the problem could be? Also, this is just a weird thing, not really a problem, but I have it set so that when it's plugged in, the screen does not dim before shutting off. Last night, I noticed that it had started to dim. I checked and the settings are still the same. Could it be related?