Question about Nintendo Switch - Grey

I would try to shut down the console completely (not just standby) and then restart it after some time (2 minutes). You can only do this in handheld mode by holding down the On/Off button for a long time.

If that doesn't help, put it back in the dock and remove it again after a few minutes to restart the display switch.

Unfortunately, I couldn't find a reset button to physically disconnect the battery.

(Only guesses, I haven't had the problem myself yet).

You are not the only one, the flickering problem seems to occur sporadically all over the world. The best thing is to report it to the customer service. After such a short time, a replacement could certainly be made. Only problem: Currently not available, so be patient :(