(I'm told that) I'm a rather dominant person in a work environment. This is a known and outspoken issue since my superior is a distant but long term friend of mine (20 years plus). From time to time I get his "complaint" that I'm not giving him the required respect. When I ask if he can give me more specific hits he struggles and refers to general explanations basically telling me to be more sensible. 

Of course my actions are never meant in disrespect but I understand how they could appear disrespectful (from his view). However when I asked a close colleague he didn't confirm my friends assessment. I only asked once so this could be by accident.

This issue did come up for quite some time, so I cant paraphrase his previous comments anymore. But today I said s.th. (don't remember what exactly something about me being less dominant) and his response was "the he doesn't know me as a person how is not dominant, he's just know situations where I'm less dominant." I'll have to raise this issue again (or wait for the next complaint) to give you a more specific version of his "explanations".

What would be a good way to approach this? I'm to solve this by changing my behaviour (I'm not planing to change his perception even if it is off unless it will be off no matter what I do).