Wheel vibration

JGreenwood07

I have a set of Avante Garde M310s on the Z and recently noticed some pretty significant vibration in the steering wheel around 40 mph. It happens sporadically, sometimes it is perfectly fine at 40 and sometimes it vibrates. The vibration also varies from slight to significant.

I have driven down specific roads and it almost seems like it happens in the same spots weirdly enough.

I am checking to see if it could be a hub centric ring issue, but also wondered if it could be the tie rod bushings or control arms? The car only has 9k miles on it and is not my daily driver. The only suspension mods include Swift springs which were installed about a year and half ago, and the car is not driven hard.

The wheels/tires were balanced about 6 months ago. My only other thought was flat spotting, but the vibration only happens at certain speeds and the car doesn't sit for more than a few days without being taken for a drive.

Thanks for any help.