My lg plasma tv get this smaal red dots over the whole screensome times this red dots are gone and then it returnswhat is the problem it is 2 and a half years old

This is a common fault on all LG sets with few people offering any solutions. I can offer a solution that could remove 95% if not 100% of the dots.
Remove the back of the set, there are about 40 screws. On the left hand side on a circuit board you will see 3 or 4 blue plastic boxes with yellow screw adjusters in them. The only 2 you are interested in are VR3 "setup" and VR2 "setdn". Mark the location with a marker pen so that you know where the factory settings were. Then turn VR3 fully clockwise. If this does not get rid completely do the same with VR2. This worked for me today, I was about to throw the TV away but I now have a 95% improved screen, sharper and more vibrant picture and saved hundreds. Hope it works.