hi, for about 2 weeks now, music from my iphoneX only emits through 1 car speaker. Any idea why?

Hi, I use my iphone X to listen to music in my car, via bluetooth. Using iOS 11.2.6. For about 3 weeks now, I can only hear music through my car's left speaker. When I shift to the car right speaker, it is completely silent. Any idea why this is happening? Thank you