Hi @lakika14 ,
You may be able to see the images on the screen better if you shine a torch at an angle close to the screen. Trying this in a darkened room will also help as they will be very faint even when using a torch.
If you have a LG 60LM6450 TV here is the [https://servlib.com/lg/tv/60lm6450-chassis-lb22e.html|service manual] that may help you to find the problem
Here’s the [https://servlib.com/lg/tv/60lm6450-chassis-lb22e.html?start=43|No video / normal audio troubleshooting flowchart] which may be a good place to start with, when the problem occurs
[https://servlib.com/lg/tv/60lm6450-chassis-lb22e.html?start=59|Here] is the section that shows the power board voltages.