This is bizzare, I am have the same issue since around the same time as you, and for me it ONLY happens on 2FM.
I'm in an E63 645ci. I also have a dension which I fitted myself and thought it may be that but it only happens on 2FM not on any other station that I'd listen to, not on CD, not on aux, not on the bluetooth either (in saying that I never listen to newstalk bar off the ball, I hate listening to politics/news radio in the car, it increases anger levels exponentially!).

I did change the set frequency of 2FM and it was still happening. I never tried turing off RDS, I'll do that later today.
One last thing and I could be imagining it but it always seems to happen when I drive the M50 every day and especially as I'm about to pass under or after I've passed under, a bridge over the road. This might link to the RDS idea.

And my missus thought I was going mad.......I'm not the only one!!