N55 noise?

[Sarreguin85]

Hey everyone, so I recently purchased a 2011 135i, with 125k on the Odometer. It had every option I wanted out of the car and it was a very good price so it was hard to pass up on it. Anyways, so recently it's started making this noise sometimes on semi-cold starts. It is very intermittent and happens at random. I've noticed it only ever seems to happen when the car has been sitting for about 2 hours after shutting off, since it doesn't happen on cold start. It does seem to change with RPM, but it goes away when the car is warm/revved up. It also occurs from 900-1500 rpm, nowhere else do I notice it. Car has had its oil changed every 10k, had dealer service it's whole life, and has never been modified. What gives? The only thing I can compare it (sound wise) is like a halfway between lifter tick and rod knock. But as I said, the fact that it doesn't happen hot and isn't consistent makes me think it's not that