2012, 84k, and standard transmission. It's a loud rattle almost like the car doesn't want to start. But once it starts it's fine. And i think the dealer is wrong because, i think it would happen every time i start it.
It would help if the dealer could show you what they see......I have had mounts that were so degraded that engine hard parts rattled against the chassis during start up....the mounts actually allowed the engine to settle too low in the chassis.
Can you reproduce a similar sound with the engine running, by hitting and releasing the throttle?
If not, how about this.....rolling in first, nail the throttle say to 3k rpm and then release it......a degraded mount will usually allow a clank on accel or decel.
My next thought is, you may be hearing the dual mass flywheel at early stages of failure......engine start up shudder is rather violent, in particular with a 4 cyl, and this may be making the flywheel rattle.
If a flywheel is failing, it (and only it) is covered as a powertrain failure.
Best I can offer at this distance.
Rob