[Ducati] front end shake

[Thurmans]

Fellow members,

I hope it is okay to ask a question about my 86 BMW r80rt.

What would cause front end shake when letting go of the bars at about 30 
miles an hour?
It surprised me when it happened.
I was able to grab the bars and it went away but now I'm nervous.

I bought it a couple of weeks ago and haven't gotten on the BMW group 
yet even though I've applied for mrmbership.

Thanks for the feedback,
Darrel