The others have already asked the valid questions, as to what your purpose for the martial arts training would be. It's a very good question, since they may be able to point out a specific style, or even school, that could fit you quite well.
Despite this, though, you don't need to answer that question just yet. You could certainly start in the martial arts, and as you develop a bit more, find out what it's all about, and what you expect to gain from it.
I'll give you a bit of info that was passed onto me by all of my teachers. A well-balanced style of martial arts is going to work both the lower and upper body. Even though many Karate styles put a greater emphasis on hand techniques compared to kicking, you will still learn how to use your lower body strength to your advantage when executing these hand techniques. In addition to this, the lower body techniques (kicking, for example), will still be taught.
I'm going to simply suggest that you take a look at various Karate schools. Simply watch a beginner, intermediate, and advanced class, and tell us what you saw, what you liked, what you didn't like, etc. If you really liked what you saw, then take a trial lesson. If you liked that lesson, then you should go further.
Scouting out various schools can be a very rewarding experience. You'll get to see how different schools teach their methods, what kind of people they have, etc. Listen to your sixth sense. If it tells you that something is horribly wrong, then just walk away from that school.