All of the racing is based on skill, so beginners race beginners, slower guys race slower guys, etc... That way, it's always fun and you are always competitive.
Don't be shy. It's A LOT of fun. I know a guy who started racing in his mid 40s...and in his second season he's kicking butt. In an email conversation just yesterday he wrote, "I wish I had found this sport 30 years ago." He loves it.
The cool thing about track racing, just like track and field, there is something for everyone. If you have lots of endurance, there are endurance races. If you are low on endurance but have sprint speed, there are sprint races. If you are all-around, there are middle distance races, etc...
It's really fun and great exercise for people of all ages. I've been in races where the youngest rider was in his early 20s and the oldest was over 60. Look at TT. Just because he's ugly doesn't mean he's slow (just kidding TT)
I forgot to address how to start.
Which track will be your local track? Some have very good websites, facebook, twitter, etc... some do not. If it's very organized, inquire about the next Track Certification Class also called Beginner Classes. This class is a very rudimentary (read: beginner) course on track rules and etiquette so that you'll know what to expect and what is expected of you. EVERYBODY must (or at least should) take these classes. I know guys who are semi-pro road racers that had to take the Certification classes. It's not to make you faster, it's simply to explain how things work. Think of it as Track Orientation Sessions.