Interesting, I have also noticed this occasionally. The other day I turned off my system, shut it down, put it into my laptop bag, and in the backpack it went. After walking for about 20 mins downtown, I felt my back starting to sweat. I took out my computer, and yeah, it was HOT, not warm, but hot. I thought I might have spilled a little water on it and begin to panic. I turned it on, and it still worked. it started to slowly cool when I took it out of the bag. I have no idea what the problem was, maybe friction? It is strange though for sure. I have also noticed that sometimes when i resume a session, ( open the lid ) after making the system sleep by shutting the lid, I get a notification that says "other users may be logged onto this computer at this time, shutting down may cause them to lose data. " No idea what this means.