Rick,
That oscillation is a very common thing on many bikes... I've had quite a few bikes and a few of them have had this anomaly, although mine have always been most noticeable while slowing down and between 40-30mph with no hands on the bars... yeah, we've all done it haven't we!
Generally you'll not notice it as the grip you have on the bars acts as a damper, and the oscillations really aren't strong enough to be noticed unless there's no controlling force i.e.
you!
I think most of the time it's caused by tyres and profiles, and occasionally you'll find a bike that's rock solid on Dunlops might develop this little wobble with Bridgstones - I certainly had that with my Pan European.
I'd start to worry if the oscillations become so severe that you can feel them through the bars, or if they happen at higher road speeds - this is definitely a sign that there's something wrong.
If this is the case then I'd start with looking at the front wheel bearings and the headstock bearings - ask Paddy how his felt with the failed headstock bearings...
AFAIK - if you have a problem with your rear bearings then the bike will feel kind of 'smeary' in a turn, almost like a drift of the rear when you're cornering. If a front bearing fails, then it allows the wheel to wobble a fair bit which will give exactly the kind of problem you've described, but it probably won't be speed dependant.
You can check the front easily but will need to prop the bike up on the bash plate to keep the front wheel off the ground. Let me know if you need a 'how to' ... lolz - you
were paying attention at the maintenance weekend weren't you ??
Greg