Nope. Never too old to learn martial arts.
Great way to get more mentally and physically tuned-up.
Many of them are terrific disciplines to learn.
I was involved with one Dojo and one form
of Shotokan Karate for many years, it served
me well during my years as a cop.
If i had it to do over again, I'd have actually
gone with Hapkido. Karate is largely defensive and
focuses a lot on point-fighting in the ring...
Hapkido is more street-smart and real-life applicable.
Both come with great mental disciplines,
(depending on your Sensei, of course).
Which brings up an important point.
Before choosing your Dojo, learn about the
Sensei (teacher) before joining up. Occasionally,
you do run into teachers that are a little psycho...
and MANY who claim to have certification that they
actually do not have...