Vaio shuts itself down randomly

Over the past few months, my Vaio VGN-FS840/W laptop has randomly shut itself down a few times here and there, but over the past week, it has happened 4 times! I haven't been able to identify any consistencies in what I happen to be doing at the moment that might be triggering this to happen. Then last night, the computer went into sleep mode (or so I thought) and I didn't touch it again until this morning, but when I went to "wake it up", the screen was just black even though it sounded as though the computer was still running. I pressed the "power" button, which I have set to put the laptop into sleep mode and it ended up restarting itself. I'm so confused as to what could be causing this. I haven't found any viruses after doing regular scans. Help please?

 

Could be possibly overheating. Check to see if fan is working and get the dust from the ports cleaned out. I have the same problem and it's overheating due to the fan being plugged with lint, etc.

 

I agree, as ive said in other sony vaio related topics, I happen to own one or rather it's my girlfriends; This does sound like a heat issue.