I can think of a few things that can have that effect on people -

- very expressive, intense tone of voice, lots of dynamics and pitch changes
- expressing intense feelings
- opinions about hot topics, especially if you brought them up
- your facial expressions
- how unexpected your subject/opinion was, given the context
- gestures such as waving your arms

Would any of these be relevant? If you mirror the other person's tone and style, you won't get this as much, keeping in mind that different people have very different norms about expressing things and different cultural attitudes about directness or tolerance of difference. Of course if this is happening at work, often a bland and professional demeanour is expected.