Took my 2008 Sidewalk to the car wash, and on the way home, the horn started blowing by itself. First a couple of toots, then steady. I pulled over, couldn’t find the fuse box and it eventually blew a fuse. Took it to my non-Mini mechanic who said the horn button was a little sticky, but he could not find the reason for the problem. He replaced the fuse and it worked fine for a few weeks. One day last week it tooted a couple of times on its own again, and I immediately pulled the fuse. Anyone else experience this or any ideas what might be causing this and how to fix it?

Currently hornless.

Probably your horn button. Horn circuits are very simple. Horn can’t blow unless it gets power and that power can only come through the horn button/switch.