The Third Doctor was played by Jon Pertwee from 1970 to 1974. The stories of this era often found the Doctor stranded on Earth and forced to work with the para-military organization U.N.I.T. to defeat the monsters and aliens that were coming to call. With such a milieu, it's probably no surprise that the Third Doctor ended up channeling a bit of James Bond and Austin Powers -- i.e., dapper clothes, karate chops, and a fancy car.
Despite being slightly older in appearance than his previous incarnation, the Third Doctor was a bit less of an absent-minded hobo and more of a take-charge action hero. He stood his ground against U.N.I.T.'s Brigadier Lethbridge-Stewart (who would nevertheless remain a good friend of the Doctor's over the decades) when necessary, and he protected his female companions gallantly. I haven't yet seen any of his adventures beyond some brief clips.
"Courage isn't just a matter of not being frightened, you know. It's being afraid and doing what you have to do anyway."
"A straight line may be the shortest distance between two points, but it is by no means the most interesting."
The Third Doctor is a LIBRA. A list of traits for this sign that I found online began with the four words "Diplomatic, urbane, romantic, and charming." Certainly seems on-target for the dashing dandy that this Doctor appeared to be! Libras are supposed to be all about harmony, balance, and maintaining good relationships, and this era certainly saw an increase in group collaboration for the Doctor, too.
The suggested New Year's Resolution for the Libra is to embrace intensity -- i.e., to let your hair down once in a while and stop trying to keep everything in a harmonious state of, well, balance (Libra the scales, duh). The ancient Greek oracle at Delphi had two mottos written in stone: one was the infamous "Know Thyself," and the other was "Nothing in Excess." Libras might think they have that second one covered automatically. However, if you're always keeping an even keel and never letting the boat rock around once in a while, that's a form of excess, too! :-)
[See the introduction for more about sources and motivations for this series of posts.]