I have been dealing with this issue for a few years. Same thing as has been described -- car shaking a little while stopped in drive which goes away when the engine is unloaded by shifting to neutral.

Recently I was driving on the highway and got a check engine light with the car all of a sudden shuddering under acceleration, extremely lumpy idle, was able to get home fortunately and parked the car. The next morning the SES light was off and the car was back to normal. Codes revealed a cylinder 6 misfire.

I took the car to my indy and he said that compression check was OK with all cylinders at about 175 except for #1 at 150. He said he wasn't sure but thought that the ignition coil of #6 had a hiccup. The coils were 21 years old, car has 204,000 miles on it.

Long story short, all the coils were replaced and now the car idles completely smoothly in drive. So, it was malfunctioning coils all along, they just weren't bad enough to trigger a code.

I think that the ignition coils should probably be considered a routine maintenance items, like spark plugs, and replaced every 100,000 miles along with the plugs.

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Mark
2001 3.0 Original Owner, still going
2012 E70 xDrive 35i Pre-Owned -- sold because no one could figure out the transmission problem