I have borrowed a stethoscope and done a little bit of poking around. The sound is almost completely not existent if I touch the engine block with the probe, it is most pronounced on the solid metal thing in the middle of the air intake (marked on the attachment).
I think it is some throttle control component. I have got no idea why it would generate such a regular sound when I’m not even touching the throttle pedal.
I’m a little bit less concerned now, I don’t have much experience with repairs but in case it fails it looks more approachable than the engine.