Laptop keyboard

Sir,
I have a samsung RV513 laptop which i purchased 2 years before. Now i encounter a problem in it's keyboard. When i press some key it never works but after a while it starts to work and, again it doesn't work. This keeps repeating with different keys. No specific key has the continuous problem of not responding. Sometimes without pressing any key it types on its own in Microsoft word. I don't know what is going on with the keyboard. Please help. I am running Windows 8.1 os with 2gb ram in the laptop and 320gb hard disk.i thought it is a problem of Microsoft word but this happens in every software. Please help.
Thankyou
Sachidanand Dubey.