Conditioning your mind to strategically establish a physical fitness work/reward realization is key to long-term physical and mental fitness. You are not likely to stick with an exercise routine that is not physically and mentally measurably rewarding.
Starting an exercise is a very enjoyable part of your everyday life that is easier than you think. Though there are possible reasons that hinder you to start off, it is normal to struggle in getting out of the sedentary rut despite your intention. In everything you do the biggest barrier is mental. Motivation plays an important role in one's self for as long as you are determined to improve your health that will improve your energy, mood, sleep and reduce your anxiety and depression. Keeping in shape will overcome all those obstacles as long as you have the right mindset and a smart approach. Always remember there is no shortcut in keeping fit instead focus on consistency.
Fitness is for everyone. Whatever your fitness level or age you have to make exercise encouraging and enjoyable. Anything that keeps you moving will work. Consistent exercise will improve your mood and energy levels that will happen instantly but the physical payoff will come in time.