Miradus... how old is he? Did you have him from a pup, or adopt him as an older dog?
I've seen dogs like this, but haven't ever had one.. we did have an Aussie/BC cross once who could have turned into a "fear biter" because she was extremely timid, but at least she didn't start dribbling if you looked at her wrong, or paid attention to her!
Are there any times he doesn't do it? Or times it always happens?
Summerthyme