Acer aspire 5100 switches off suddenly

I have acer aspire 5100 laptop running fine from last 1 yr. just 2 days ago i have encountered a problem with the laptop.Its switching off suddenly after every 10 min. i have been using the laptop for the last 1 yr without any problem and in the past i have used my laptop continously for more than 1 week without switching off.The laptop doesn’t even seem to be over heated as the back of my laptop is quit cool.