My phone is Nokia 35oo .When I switch on phone it automatically pressing the buttons espicially 3&6 buttons by no of times
And no other buttons are working espicially OK button,green button etc..
What the problm was??

It sounds like the phone may have been damaged by water, I've seen this happen many times. If you're up to date on payment I would recommend bringing the phone to your carrier so their tech support can look at it for you. -CsX