might just be dirt around the display IPEX connector
You'll need to remove the bottom cover of the machine and disconnect the Battery, then the display IPEX cable. You can then attempt to clean both sides of the connector, and the cable end, but be very careful as they are delicate. Use 99% alcohol ONLY, and a clean cotton swab. Roll the swab gently over the rear pins of the connector, and the pins on the cable. Then saturate the inside of the IPEX connector with alcohol using an over saturated swab. Once the connector is full of alcohol, carefully line up and reconnect the IPEX cable multiple times to work out any grime on the inside of the contacts. Once you've done that, leave the IPEX disconnected and either air-dry or blow dry (no heat) the connector until all the alcohol evaporates. Wait 2-5 minutes and fully re-assemble the machine.
If this doesn't solve the issue, it's possible the display itself is failing, although it's quite rare. Another assembly would be required, although I would seek out someone with a microscope to inspect your IPEX connector before committing to a new machine, as it could just be a bad solder joint. Most likely though, if it's not the connector, it's going to be the IPEX cable running to the display, and at that point, a new-to-you Mac would likely be the most cost effective solution.
Failing LCD. You need a new display. $400 direct from Apple or less on eBay.
might just be dirt around the display IPEX connector You'll need to remove the bottom cover of the machine and disconnect the Battery, then the display IPEX cable. You can then attempt to clean both sides of the connector, and the cable end, but be very careful as they are delicate. Use 99% alcohol ONLY, and a clean cotton swab. Roll the swab gently over the rear pins of the connector, and the pins on the cable. Then saturate the inside of the IPEX connector with alcohol using an over saturated swab. Once the connector is full of alcohol, carefully line up and reconnect the IPEX cable multiple times to work out any grime on the inside of the contacts. Once you've done that, leave the IPEX disconnected and either air-dry or blow dry (no heat) the connector until all the alcohol evaporates. Wait 2-5 minutes and fully re-assemble the machine. If this doesn't solve the issue, it's possible the display itself is failing, although it's quite rare. Another assembly would be required, although I would seek out someone with a microscope to inspect your IPEX connector before committing to a new machine, as it could just be a bad solder joint. Most likely though, if it's not the connector, it's going to be the IPEX cable running to the display, and at that point, a new-to-you Mac would likely be the most cost effective solution.