Hi there ~
I understand your concern. Humming all the time at work is a sign of happiness, and if you are doing it involuntarily and not considering the people around you especially if you are around a boss and are still doing it, it might be an obsessive compulsive disorder
, the obsession being the need to vent things out in the form of humming and the compulsion being humming. I also think that you might need to visit with a psychiatrist
I hope this helps. Take care and have a lovely day!