Did you drop your laptop or split anything on the keyboard?
It looks like you have internal connection issues between keyboard and motherboard, As Lemanoj suggested try to use External keyboard, if it works good then it is surely keyboard issue!
I have also encountered that problem in my acer netbook so I have tried using a external keyboard. After using another keyboard and disabling the built in keyboard that problem didn't occur anymore. So I bought another built in keyboard for my netbook and replaced the defective one and then my problem is solved. I hope this will help you!!!