Yep it's the well known screen flicker problem. I don't think it's related to heat actually I'm not sure what causes it but wiggling the hinge a little (a little!) sometimes makes it stop. Anyway, at only 3 months old your computer is still under warranty and Sony will replace the screen so just boogie on over to the phone and give them a call.
www.vaio-link.com has the numbers.
Edit: Actually I have a question......do you have a reliable way of making it do this? Sometimes mine can go for days without doing it then suddenly spasm out on me. One of the problems people have found is that when they send computers off to be fixed, the problem doesn't happen and it gets sent back to them because 'nothing is wrong'. It's one of the reasons I haven't sent mine off for repair yet. Unless you sit and look at the screen for hours every day you might never see it 
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