very intermittent, very bad shimmy

I'm done many searches, but cannot seem to find an existing thread regarding this -

Twice in the past 6 weeks I've been driving at about 60 mph when suddenly a violent shimmy starts, like if a wheel weight was suddenly lost, seemingly from the front right tire. I stop, look at the tires to see that there is nothing obviously wrong, then start up again and drive 30 more miles at speed with absolutely no problem. Between these two events, I have driven the freeway with no problem.

It seems with most front end issues the shimmy is consistently present at certain speeds, but that is not the case with this. It is strange how bad the shimmy is, to only go away without anything mechanically changing. Otherwise the car drives fine.

The car was in for an alignment about 2 months ago at the BMW dealer (due to a tire wear issue), and they indicated they did their 'multipoint' inspection, so I would guess if there was any obvious front end issues they would have flagged it and offered to fix it for me (kind of the purpose of the free inspection, I suppose).

I am running snow tires with aftermarket alloy rims. In both cases there was not snow lodged in the rims.

2002 325i with sport package

Any ideas would be appreciated.

Search on control arms and fcab or front control arm bushings.

Sent from my DROID X2 using Bimmer

Thanks for the response.

I have reviewed many of those posts, and perhaps that is what it is, but what throws me is that symptoms described in those posts refer to consistent issues, not random ones.

if they haven't been changed for around 2 years, they're probably due to change and might be causing these issues (might be first signs)

I had it at the dealer for a different issue, and explained the shimmy symptoms. They checked over the front suspention and could not find anything to replace. The mechanic's best guess given the intermitten nature of the problem was that the caliper may have stuck enough those two two random times, and by stopping it unstuck. I've had sticking calipers years ago on an Acura, but they did not let go. I will check the wheel for excess heat if the shimmy happens again.

I replaced the front pad and rotors a year or two ago, but did not replace the pins the calipers slide on - I guess I could pull it apart and make sure it all looks okay.