picture off and on sound ok

Try several sources, all direct wired. I’ll assume you’re using HDMI. If issue persists, use a flashlight to see if it’s a backlight problem (I doubt it). If issue goes away, especially on more than one source, something between source and display isn’t compatible with the source HDMI stream. Saw this on an older AV rcvr w/HDMI switching. Turned out the rcvr version of HDMI processing was too down rev to handle the source bit rate. Display would go all black, or white intermittently. Bypasssing the rcvr worked fine.