Job interviews are tough, often because we judge ourselves too harshly throughout the process and end up altering our behaviour for the worst. Chances are those long pauses you take and reserved, comfortable body language you provide are actually good.
To prove it, Redditor edlorenz7 suggests recording yourself in a practice interview before you go:
You may fear that your pauses are too long, but that's rarely a concern. If you're prepping for an interview, record yourself and listen. You'll notice that those pauses aren't really as long as you think.
The same goes for visual cues, so stick a video camera on yourself to see how you actually behave. You may find everything you do is better than you expected. If not, you'll know the exact problem because you can see it, hear it and then correct it for the actual interview.