Car door interior lights blink on and off

Welcome to 2CarPros. It likely isn't the fuse as most interior lights share a fuse with other circuits. I would start by opening and closing every door a couple times and as you do that feel if the door is loose or has movement while closed. That is because the switch that controls the interior lights is activated by a switch in the door pillar, if the door can move much it could be flashing the lights. Next open each door and look for the switch, It will be on the pillar to the rear of each door. See if one feels loose or sloppy.
The lights are turned on when the switch grounds the brown wire, it could also be that the brown wire is broken inside a door or flex area and is grounding that way. The easy way to tell what is the problem is to pick a door, remove the screw that holds the switch in and remove the switch. Pull it out and be sure there are 2 wires attached in the connector. Nor remove the connector and tape it so it cannot fall through the hole. Take the car for a drive and see if the lights still flash. If they do remove the next door switch. Don't remove them all at the same time. The one you remove that stops the flashing is the bad switch. Now if you find one with a broken or missing brown wire, the wire likely came free and is grounding out inside the door. That requires removal of the door trim and fishing the wire back out to repair it.