mine started at 10k miles. Premium fuel made no difference. Mine is sporadic. only when hot though. I think its a lean condition....just a guess though....
I’m thinking lean running condition as well, has to be something with the ECU, intake manifold or throttle plate, I don’t think it’s ignition or fuel related but it’s driving me crazy. Dealer said they couldn’t replicate the condition, I had an O2 sensor code (P0137, Bank 1 Sensor 2 low voltage) which they shrugged off and reset, said it was a fluke but it’s definitely sensing something is up. I notice it after cold start especially but it will do it when hot after it’s been sitting for awhile too. I wonder if disconnecting the O2 sensors will clear it up? I wouldn’t run it that way for long but just to test things out I might try it.