Do I need to get in shape before I start?

This is the most common reason people wait, and it is the wrong way round. You do not get in shape and then come train. You come train, and that is how you get in shape. In fighting shape, which is a different animal to treadmill shape.

I turned pro in mixed martial arts at 42. I have coached people who had never done anything athletic in their lives, people carrying injuries, and people who had not moved properly in twenty years. One on one means the pace is set by your lungs, not by the fittest person in the room.

Here is what the first month actually feels like. You will be out of breath sooner than you expect and sore in places you had forgotten about. Both fade. I work in short rounds with real rest, so you are learning in the gaps instead of just surviving them. If you need to sit down, you sit down. Nobody is watching but the coach you called. How sore you should expect to be covers what is normal and what is not.

Weight is not a barrier either. Grappling in particular rewards heavy and calm over light and frantic, and there is a whole answer about where to start if you are carrying extra weight.

Tell me what your body is doing right now. The bad knee, the back, the asthma, the surgery last year. I plan around it. I am a coach, not a doctor, so anything medical goes past your doctor first.

If it is the conditioning side you want specifically, that is what FightFit is: circuits built out of fight training instead of a treadmill. See what you can train.

The fitness turns up as a side effect. Nobody trains twice a week for three months and stays the same shape, and none of them got there by doing cardio first.