BMW 320d slippage between 1700-2000 rpm

I live in Germany and have 2001 BMW 320d touring (2.0 L diesel E46) with a 5 speed transmission. I bought the car about 2 years ago and have had to get numerous items repaired including wheel bearings, brakes, etc. leading me to believe that the previous owner drove the vehicle fairly hard on the autobahn. Recently, the car has begun to feel like it is slipping around the 1700-2000 rpm range, especially in 1st and 2nd gear. The slippage is noticeable in all gears now at the same RPM range, but there is no accompanying spike in RPMs that would be indicative of a typical worn out clutch; the car just jerks a little bit. As soon as some throttle is applied, the slippage seems to go away. Since I have owned the car, the clutch has always juddered a bit during initial grab in 1st gear, but I assumed it was just characteristic for this clutch/motor combination. Other discussion I have read on this vehicle indicate that this is a sign of the self adjusting clutch going bad. Basically, I want to think that this is a worn out clutch issue, but it does not behave like other clutch problems i have had with other vehicles. Furthermore, sometimes the slippage is very noticeable (e.g. the car will barely move in 1st gear) and sometimes it seems to not occur. In fact, when I took it to a mechanic, they said that they could feel nothing wrong with it. I don’t want to throw money at the wrong problem as I have already spent a considerable amount on other repairs to this vehicle; any help would be appreciated.

I believe you are correct about the car probably being driven hard, and I think that maybe the clutch has been overheated and the flywheel and pressure plate are blued and glazed. To get a good clutch feel, the clutch may need to be replaced and flywheel turned or replaced. There is no way to drive out a blued flywheel, it must be turned.

I would also worry about a driveability issue instead. In other words, you might be having an engine performance problem rather than a driveline problem. E.g. one thing that will often coincide with that same rpm range is a particular throttle position, and a throttle position sensor with a flat/dead spot will make for problems. But there are lots of possibilities. Is it safe to assume that there are no warning lights on the dash? If there are, have the error codes read and post them.

My thinking is along the same lines as Cigroller.
The specific RPMs are–IMHO–a clue that this problem is more likely to be engine-related than anything to do with the clutch.

In addition to the throttle position sensor, it might be a good idea to take a look at the MAF.

I have read that this particular motor may have an issue as described, but there are no glaring indications that this is the culprit. No warning lights or anything of that nature, but the performance indicators do seem more indicative of an engine issue. For example, from a cold start, if I do a normal slow acceleration, the lag is extremely noticeable in the previously mentioned RPM range whereas if I goose the gas pedal, the car behaves normally for all intents and purposes. Similarly, if I set the cruise control in that RPM range, I will feel a very noticeable jerking sensation whereas if I set it slightly outside those ranges, no problems.

Do the tree test to see if the clutch is gone. I think you have unrealistic expectations if you think replacing brakes and wheel bearings is unusual on a 13 year old car you have been driving for 2 years.