Macbook White SOS code beeps on startup

Hello,

When I try to start my MacBook I hear a SOS Morse code. I solved once by throwing it on my bed but then he does not do it again. Maybe someone knows what is going on and how to fix this?

Perhaps this useful information:

Apple MacBook White 2.2 Ghz

Model Number A1181

Mac OS X 10.7.5

2 GB RAM DDR2

Intel Core 2 Duo 2.2 Ghz

120 GB HDD

(Everything is translated with Google Translate, even the title)