DIAGNOSIS This is usually a HDMI handshake issue. When your PS5 changes its output resolution or refresh rate (like going from a game menu at 60Hz to a game at 120Hz VRR), the TV and console sometimes fail to re-establish the connection smoothly.
FIX Enable HDMI Deep Color and set the input icon to 'Game Console' or 'PC' for that HDMI port. Go to Settings > All Settings > Connection > HDMI Settings. For the PS5's port, turn on 'HDMI Deep Colour'. Then, in the Home Dashboard, edit the input icon and select the correct device type. This tells the TV to expect a modern gaming signal and can stabilize the handshake.
IF THAT DIDN'T WORK The culprit is often the HDMI cable itself. You need a certified Ultra High Speed HDMI cable (the one that came with the PS5 is good). Cheap or older 'high speed' cables can't reliably handle the bandwidth of 4K 120Hz VRR signals, causing dropouts. Try a different, known-good Ultra High Speed cable.
HEADS UP Don't just keep swapping inputs or turning things off and on. A bad or marginal cable can cause these intermittent dropouts and also potentially damage the HDMI port circuitry over time due to signal reflection. Use a proper cable.