Following is from documentation that I did for feedback on my 97 540i/A. My interior is now "dead quiet" but I do have to treat the leather seats about once a month - others have said similar about the leather

CABIN NOISES, and solutions

In many cases I applied lubrication in the locations where plastic components rubbed on themselves, or on metal or leather. The lubricant I used is called “Super Lub”. It is a Teflon based gel lubricant that apparently stays in place, does not deteriorate, and is not affected by heat or cold. It was also recommended for use on disk brake components.
It is also available in a spray format

Note - this is teflon, not silicone which should not be used.

Front seats:
1. Clicking sounds returned - bushings at the front required further lubrication (bushings need to be taken apart to do this).
2. Buzzing of the plastic seat rail covers - put small foam blocks under the rails (down by hte floor).
3. Creaking sound in back of driver’s seat - found several wire clips/springs squeaking when moved - lubricated.
4. Seat back panels loose enough to move against leather. Dented the brackets on the inside of the panels to more securely hold the mounting clips. On the passenger seat the plastic bracket clip inserts were missing for the upper panel.
Tightened and lubricated all mounting clips.

Rear Seat and Package shelf
1. The rear folding leather seats “creak”, because they move with road vibrations. There is “play” in the bolt fasteners at the hinge points. I applied a wrap of tape to the outboard bushings to decrease the play in the body bracket, and I inserted teflon sheet material as a shim in the centre bracket to remove the play.

2. The 4 clips at the rear of the package shelf were not screwed down tightly, and one was actually turned sideways so that the vent tab was not in the clip. This allowed the rear of the shelf to vibrate.

3. There was a rattle in the sun blind occurring at the 3 “contact points” between the 4 bolts. I corrected this by inserting thin cloth insulators at these points. Also a friction fastener had fallen off the sunblind, and was loose on top of the plastic speaker housing.

4. There was a vibration in the upper brake light housing - corrected with silicon caulking along the lower gap between the lens & housing.

5. There are several plastic panels that move slightly against the metal package shelf, resulting in creaking noises. The main problems are the hard plastic bottom on the sound deadening cover for the shelf, and the upper trim panel behind the rear seats. I placed some cloth material between the panels and the body to eliminate this.

6. The speaker grills produced slight vibration sounds at times. I installed small foam pads under the grills. (glued to package shelf)

Door Panels - This apples to all door panels except where otherwise specified:
1. Creaking sounds from doors on small bumps, etc. - removed all panels and trim components. Lubricated “all points of contact” including clips and fasteners. The outer edge of the panel is where most noises were occurring.
2. Driver’s door had a wind noise, and cold air, at the rear lower corner. There was also cold air coming through the window control switch box in the winter. I found the interior sound/weather panel to be unsealed at several locations. I resealed it around the perimeter and also sealed the holes where the latch cable and wiring come through the panel.
3. The new seals along the top of the door are better than the old ones, but still creak at times. I finally solved this when I pulled them off and lubricated the underside of them (between the seal and the mounting surface)
4. The air ducts to the front doors are met with a round rubber-sealing ring on the body. This ring creaks against the door, and it’s own mounting surface - lubricated.

SunRoof
For as long as I have had the car there has been a “clicking” sound coming from the area of the sunroof - seemed to be from the rear passenger side. It occurred all the time, "except" when the roof was tilted up.
I finally was able to reproduce the clicking by moving the front of the open roof up and down a bit. The clicking was coming from the driver’s side, and using a stethoscope I was able to pinpoint it to the tilt hinge at the front of the sunroof. After application of spray lubricant it has been completely quiet for 2 months.

Dash
There were various components that caused noises in the dash. Some were minor, but added to the “symphony”.

1. Cracking sound around the dash/windshield area. It would occur when turning or braking - but only at times.
Others started talking about the same item on the digest, and someone chimed in that their BMW dealer (USA somewhere) said it was quite common and that it was the “earth pin” bolts in the hood hinge.
I lubricated and adjusted mine, as the guy recommended - NO MORE CRACKING SOUNDS!

2. Faint buzzing sound in lower centre console. Traced to the keys rattling in several of the switches (ASC was the worst). Opened and applied lubricant to the interior surfaces.

3. Faint buzzing in the overhead panel. Traced to the relay on the circuit board of the sunroof control module. This is a sealed unit therefore I did not attempt to fix.

4. Creaking sounds from the centre dash whenever sun shone on that area. Traced to the climate control unit - it is a tight fit and it expands quickly when in sunshine. Applied lubricant around its perimeter.

5. Metallic vibration from the lower dash in front of driver. Traced to the metal knee bolster unit inside the dash. It resonates with certain road vibrations. Put some small pieces of foam rubber inside to dampen the vibrations.

6. There were also several other small components under the dash that could be made to vibrate when tapped. I used small pieces of foam to cushion and support various components.

7. I also looked into the trunk area for sources of noise. I found various plastic components that creaked etc.
- The plastic subfloor creaked in various spots - I lubricated all contact points including the rubber supports underneath (some were missing).
- The rear panel needed lubrication at various points.
- The rear deck creaked loudly whenever slight pressure was placed on it (like washing / waxing). I removed the inner cover and found that the caulking beads between the inner shell and the outer skin were separated in several locations. They would creak loudly whenever they came together and separated - I assume this would occur as the outer skin flexed on bumps. I filled the gaps with silicone caulking. (I then checked the hood and found the same situation).