Since your 38 (I'm 37 myself), I would suggest to start with only grappling or only striking for minimum the first four years.
Originally Posted by Dr. Whom
Later on you can start training in the other.
For grappling: BJJ and 10th PJJ are closely related (10th PJJ is just a unorthodox no-gi version of BJJ).
For striking: Muay Thai and Savate are perfect complimentary arts, but if you think for now that your overal fitness level isn't good enough for Muay Thai than I have some bad news for you.
Savate requires even a higher level of fitness and condition: it's 50/50 with kicks and strikes, clinching is not allowed and you have to constantly move around your opponent at a high level pace or you will get cornered hard.
Pick something, enjoy your training and don't make it your life's mission to become a badass. Badassiness is a side-effect of having fun at training, going on a regular base and not getting frustrated when it looks like you have reached a certain plateau in your training. You will surpass these plateau's from one to the moment after being stuck on one for a certain time without even knowing how you did that. ;-)
Hope that this helps,
On that I agree.
Originally Posted by Permalost
Try them all. Take it slow. See which one feels right and comfortable. Then train that one. Better to master one thing than to know a little about alot of things.