I would say start now. I mean, why not? If you aren't planning on doing it or are physically limited that's one thing, but you say you will start eventually, soooo.. what are you waiting for?
I started right away because I was so focused on losing weight and exercising was a wonderful outlet for my frustration
I will get into lulls where I will go a week or two (although that is very rare), but I have consitently exercised since I began my journey. I began on the elliptical and with the weight machines at the gym where I worked. I was also recovering from shattering my ankle and the subsequent surgeries (long version of this story is linked in my sig).
I basically continued with this routine for a couple of years. I incorperated hand weights and found them more effective and also began working on the big ball. I also started dropping in on classes (Yoga, Nia), which I still do.
A couple of years after I began my journey and long after I hit goal I began running. My schedule now invloves just about everything under the sun. A few months ago I met with a trainer who helped me find som new moves
The past few weeks I have been powerwalking with my dog, using resistence bands, 30-40 minutes on the elliptical along with some random stuff my trainer has been showing me.