Horn comes on on its own whether in the car or not

This morning I was driving down the street and the horn came on steady for 20 seconds onj its own. Latewr in the day when the car was parked for four hours, somebody told me that the car horn was intermittently sounding itself while parked as if the alarm had gone off.
Then, later in the afternoon, while the car is parked , I hear a beep or two once or twice an hour and sometimes a 10 second blast.
What would cause this horn to act up.? it is almost like their is a ghost in the car toying with me. What a coincidence that it is Halloween today.
I do not know where to begin to solve this issue other than pulling the fuse or relay whichever could be causing this. Any suggestions?