I think silence is only ever awkward if you apply the label "awkward" yourself though. I mean, I'm sure you've been in a situation where things were naturally quiet but you were so wrapped up in thought that you didn't consider the silence to be oppressive. I noticed that myself just now as I took a drive with my dad. I didn't say much, but it was totally okay because we're on a similar level, comfortable, and were probably caught up in our own little mental worlds at the time. That to me says a person is in control, that they can condition themselves to be at ease with silence. As for your breathing and swallowing, well, you're only human. I doubt others perceive it to be any worse than coughing or sneezing for example. SA/SP can really make you paranoid about those sorts of trivialities, though.