Sony Cyber-shot DSC W170 lens going on and out while I turn it on

Sony Cyber-shot DSC W170 lens going on and out while I turn it on

I need to repair my camera ,it is the lens that moves to extend but it is going back aagain .The screen is working and it show error to turn it off and on again but after i did that it still the same, please aswer me to fix it i knew that it is asimple problem and i may be to clean the lens but please tell me the steps