MacBook won't charge iPhone properly?

When plugging a lightning to USB cord into my MacBook and iPhone, my iPhone vibrates rapidly and flashes the charging icon. This process repeats continuously unless I unplug it from the Mac. In addition, macOS brings up a software update to 'connect to iPhone', which I did with no luck. An Apple support representative informed me that I would need to visit an Apple store (not an option due to location) or mail-in my device. I think both of these options seem extreme. I've seen similar issues with the same MacBook Air but an older iPhone. Not sure what to do.

Hardware: MacBook Air (Late 2015), iPhone X

Software: macOS High Sierra 10.13.6, iOS 11.4.1