I think you need to follow circuitsmith’s advice and either check or have checked your charging system.
However, I do want to add appoint. I use Sylvania Silverstar Untra bulbs. They’re much, much brighter. But when putting new bulbs in a friend’s car recently I chose not to, because they only have a lifespan rating of 250 operating hours. Sylvania currently makes four different levels of headlight lamp (they used to make five), each brighter but each with a lesser lifespan. The “standard” lamp is rated at 1000 hours, mine at 250, with two in between.
The reason is that the brighter light is achieved simply by using a filament that burns hotter. A hotter filament means that it burns brighter but burns out faster. It’s a tradeoff. I think the ones I installed in my friends car had a rating of 850 hours. They were one step up in brightness from the basic lamp.
The lamps are made right here in Hillsboro, NH. I’ve toured the facility and gone over he technical docs with one of their engineers and with their HR manager. It’s cool stuff. Their incandescent home lamps used to be made in Manchester, NH. That plant is closed now. Everyone got laid off. Sigh.