Monitor blacks out occasionally

My monitor(LG Flatron E700SH) blacks out occasionally.... but when i give a thwack on the side of the monitor it come back to normal but with a little flickering and change in brightness and contrast. Some times i have to give 2 3 hits to make the monitor work.
During black out the LED on the monitor never starts blinking, i.e. signal is still there, so its some internal problem on monitor.
Experts please comment if there is anything i can do myself before giving it to the vendors for servicing.