I have lg plasma i heare clicking sound when i turn on and there still picture for few minutes and it's gone but i could still heare the sound clear.

There's a good chance you have failing electrolytic capacitors either in the power section or the inverter section or both.
Any caps in these sections that look bulged at the top, or bulged/leaking at the bottom need to be replaced.
If you repeatedly turn it on, eventually it'll probably stay on, but every time you turn it off, the TV will get harder and harder to start up until one day it just won't.
Sometimes you have to do the opposite to start it up and unplug it for 5 mins, then try.

If you aren't tech savvy, this unit needs to go in for repair.

If you are handy with a soldering iron and can identify the power supply and inverter / FM section for the backlights, an inexpensive handful of capacitors will likely fix you right up.
Match the capacitance on the capacitors. Go over voltage if you can, and still have them fit.
IE - it's not a bad idea to replace a 10V cap with a 16V or 25V or even a 50V, but don't replace a 680uF cap with a 500uF or a 1000uF (unless you are positive it's only doing ripple filtering, and even then, you should go OVER, not under the uF rating).

Most of the caps that go are 10V 1000uF or 3300uF.

I found some great videos of the procedure (for many Samsungs with the same issue) on youtube.
http://www.youtube.com/watch?v=Mm51C_RDIZE
http://www.youtube.com/watch?v=BNHHrgX_6cs&feature=related
http://www.youtube.com/watch?v=8l0AUj8QUkg&NR=1&feature=fvwp
http://www.youtube.com/watch?v=Y7b_nTaZYcU&feature=related

As you can see, this issue spans plasma TVs, as well as large and small LCD TVs and monitors.
The parts are cheap, and skill required is minimal.

Most common problem with this sets are Bad Capacitors on the power supply board, they will be vented or puffed up on Top. 2200uf 10v 3300uf 10v 1000uf 16v