[GratefulCitizen]

People who are trained/experienced in reading body language often have "tells" which reveal the fact that they're trained/experienced.

There are many, but one of the most obvious is "mirroring".
They'll mimic your posture, particularly how open or closed it is (this is often literally mirror image, left vs right).

Such people frequently have a difficult time relaxing and interacting genuinely with new acquaintances.
It's nothing personal, their apprehension is probably rooted in the same reason they acquired the training/experience.

It's possible to put them at ease.

After some interaction, demonstrate some "submissive" body language and wait for them to demonstrate something which indicates feelings of superiority.
Another alternative is to ask them to talk about something in which they have expertise.

Then they'll relax and the interaction will be more genuine.