There are many trails in Patagonia suitable for all fitness levels, as well as many better suited to experienced hikers. Notably, the region overall is not considered high-altitude, negating the need to build in adjustment days.  However, if you are embarking on a multi-day trek, it’s good to ensure you’re comfortable carrying whatever you’ll be bringing in your backpack, and conducting lots of advance research into the specifics of the trail you’d like to do is always a smart idea, as well as chatting with rangers and other hikers.  If you’re a novice, consider going for walks in your area prior to departure, and/or contacting a guide.