I think, that's not because overheating. Last night (in my place right now, It's morning), I turned on the air conditioner (It's around 22° - 16° C). I think, there is another reason of this.
*Long time ago, my laptop is shut down unexpectedly. I forget, if the situation is in the noon or night, before playing or when playing. So, this is the second time I get my laptop restarted/shutted down unexpectedly.