My brothers e46 M3 SMG has a couple problems right now.

It hessitates very badly at idle, and any rpm under 4k, and has power loss.

Also, sometimes when he turns the car off, it seems the hydraulic clutch locks the car in gear, so that sometimes all you have reverse, and when engaging first or 2nd, the car bogs down very bad, and doesn't go.  My solution to that was to turn the car off in neutral, and engage first with the stick, then you can start the car, and get all of the gears back.

This all happened during one day, without any warning, and no hard driving involved.