When you restart computer your computer gives repeating 3 beeps?
These are called "beep codes". Unfortunately you didn't give
enough information. Beep codes are in two formats, short and long.
They are in a sort of code, much like Morse code.
Are the beeps three short beeps, three long beeps, or a mix of
short - long?
Does your computer continue to boot and work normally? I
wouldn't worry about it too much if it does. Some computers beep on
initiating different components.
Listen closely and see if you can tell if it's all short, all
long or a mix, then search for beep codes and you should be able to
find what the codes mean.