It is doing what is called "indexing" which means in the head set in the last 24 years has worn out and really needs to be replaced. Sometimes you can use it a bit longer if you take it apart and put indivinual balls into the head set instead of caged bearings. It happens because most of the time when you are riding the wheel if facing straight and 24 years of road bumps have dented the bearing races. Myself I would just put a new head set on the bike. Roger