Timid. Although I'm super talkative when I'm comfortable (pretty sure nobody in nuzwriter's lounge could get me to shut up if they wanted to), I have extraordinarily bad social anxiety, to the point where just a few years ago I would burst into tears if somebody asked me to order pizza over the phone, because I couldn't say no to them but I was also afraid of talking to a stranger over the phone. To add to that, I know I don't have the same social boundaries as other people, so I tend to overcompensate and get really scared about broaching any topic that people don't bring up first.
I'm much better now, but it still usually takes a lot for me to open up (although talking about anime/video games tends to be a very helpful shortcut), hence timid.