@kamranazam if the lines are up and down then those are vertical lines. Common issue is the main board as well as the ribbon cables (there is always a chance of a bad panel as well). Remove the cables and check for tears as well as corroded ends. If the cables are good, then consider replacing the main board. This "after 15 to 20 minutes start disappearing" is possibly due to solder joints closing and making contact. Check your board for cold solder joints. You identify those by the color of the joint. It should be shiny silver, if it is dull grey, resolder it.
Let's see what those lines look like. Post an image of what your screen shows as well as your boards. that way we can see what you see. Voeg afbeeldingen toe aan een bestaande vraag
Update (07/02/24)
@kamranazam you need to check on your driver boards. Those are the boards that connect to the LCD. Those can also cause differences in color and vibrancy. The washed out display is commonly caused by issues with the Gamma IC.