Exterior AND interior lights cutting in-out intermittenly

This started a week ago. My exterior lights and interior lights (gauge lights) will cut in and out randomly. I looked on some forums and there are a few thiings people suggested but doesn't narrow anything down. I checked the battery connection. Ground wires seem to be ok. Nothing else electrical is malfunctioning. One of the mechanics said it could be my light switch itself. And some reviews online said it could be the alternator or the battery. The battery is about 4 years old now but car runs and starts fine and everything else is fine unless the battery is going bad? And the last thing I heard was the ignition switch and was wonerding if that was possible?