I used to have that problem.
I think it might have as much to do with expression as well. If you don't smile and you maintain eye contact, it's seen as intimidating.
After much practice, you kind of get into the habit of smiles, nods, looking away at scenery for a while then returning back to eye contact.
Basically, they want you to look at them and nod if you agree with what they are saying. When you talk, gesture a bit, cast your attention around the room or horizon a little, as if what you're saying isn't that important. But then listen to them when they respond with smiles and nods.
It's like a ratio that you have to fine tune and you should judge how far you go one way or the other on a situational basis.
...Oh, and mirroring. If someone smiles when talking to you, smile in pretty much the same way. If it's subtle, you smile subtly, if it's broad, go fairly broad (but don't over do it). If they are saying something serious and not smiling, don't smile. All in all, try to follow their gestures, but in a slightly more subdued fashion.
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IN GIRVM IMVS NOCTE ET CONSVMIMVR IGNI