Cold engine makes unsteady rattling sound

When the engine is really cold, starting it makes a short unsteday scratching sound. When idling (regardless if clutch is depressed or not) there is some unsteady rattling sound (like something is loose) near the side of the clutch. Any ideas?

Change: noise is gone as soon clutch pedal is depressed!!! 

After testing again I only hear the unsteady knocking sound when the clutch is released. So when I press the pedal the sound is gone. It is only when the engine is cold (first couple of minutes). I tested the car in neutral when standing still. I have no problems when driving, but it really doesn't sound ok... Do I have to search this problem in the clutch or gearbox, or....?

sounds like the release bearing on the clutch.

Should I serach the cause near the clutch or gearbox?

I'd go with the release bearing also. It could be a bit loose on the shaft and rattling against the splines on the clutch when there is no pressure on it. It would not be a job I would be in a rush to fix until it got undriveable.

Does the clutch shudder when cold when u pull away slowly? I had the same experience with an Opel once. It was the clutch pressure plate and clutch. I would say replace the clutch, pressure plate, release bearing and scim the flywheel. What it also can be is that lil bearing behind ur flywheel, just check if it okay aswell.