|Could be RAM. First step remove RAM sticks and clean their edge connectors with a soft pencil eraser. Insert them in and out a few times before pressing them firmly in place.|
Otherwise, if there is more than one stick try each one on it's own in first position to see if you can determine that one is faulty.
There are RAM tests available:
There are other possibilities but RAM appears to be the most likely.
Always pop back and let us know the outcome - thanks