Help Samsung Galaxy S opens random applications by itself (sensitive screen problem?)

[svete]

Hi

I have bought my Samsung Galaxy S1 several weeks ago. I noticed that sometimes when I unlock the phone it opens applications by itself, as if someone touches the screen. For example, I enter to contacts screen, and it starts to navigate through contacts and adding / opening them
I click on Home button, and it starts opening a browser or another application.

If I move to another place in a room, it starts to work correctly. So it may be related to environment. I have to say that the problem started almost immediately after I received it
What may be the source of th problem?

thanks for help