Any of u experience Kluck kluck sound from tranny?

[Soo]

Need help, just inherited an E28 with M30 3500cc MT engine and it seems like that there's this kluck kluck sound around the transmission and clutch. Its not that loud but enough to be heard from the inside of the car. Its usually heard when the engine is running and the car is standing still at the red light our something. But once u press the clutch, the sound goes away. Doesn't happen when u are driving, or reving the acceleration when the car is standing still. Another time when the sound can be heard is when u turn off the engine, doesn't happen if u step on the clutch and turn off the engine though. The sound doesn't seem to happen all the time just somtimes irregularly. What could this sound be from, the flywheel, clutch? Thanks.