I do this all the time, having conversations talk with my self out loud I try not to for it in public but I have been doing it at work more often
It gets bad enough that I started questioning myself if I did it when ppl are around, I think I scared one lady when I went out for a smoke and she quickly went back into the building another I saw in the smoking area just gave me a strange look.

My boyfriend told me this is usually a sign of loneliness anyone else's thoughts?

I tend to do it when really stressed or complex thinking, well wait I do bored too....
Some coworkers that know me for some times just laugh if I'm talking to a vending machine asking it why it doesn't like my money I usually try to make a joke if I'm caught, or coffee machine if I'm making a mess, again maybe humor for some, or say they don't mind, but Idk how normal is this?