Natural Introvert... I am very reserved and can still be even around people that I have know for years.
INFJ - http://www.humanmetrics.com/vocation/JCI.asp?EI=-83&SN=-88&TF=-12&JP=56
The last time I took the full Myers-Briggs almost 12 years ago and I believe I was INTJ.
But I find extraverts facsinating; mostly because I don't understand where all the energy comes from. Things such as being the life of the party or the center of attention, I find exhausting and somewhat aggravating. I have to force myself to stay in certain social situations. But when I observe individuals that are social butterflies or can hop from one cubicle to the next, socializing with everyone, I just find it amazing.
BTW - Great advice Terry, extroversion has its perks. Part of the problem I have is actually being interested in other people. A bit self-centered, I am.