This used to happen in our '88 Jetta...but only to my wife when I was not
around..hehehe...I use to laught at her when she would rant at the
car...man did I laught when watching "Little Miss Sunshine" when their
horn went off.  It is likely your horn ring.  Take your steering wheel off
and have a look at the ring and the brush.
Pascal
'84 Westy