From my experience is important to change your mind/mindset about training before you can change your body. Start small, nice and simple, very achievable and give yourself some easy wins early on to build some momentum. To create a habit you need repetition, which means an easy routine that you can build on later as the improvements and endorphins start kicking in. Once you've created the habit, your training will be like brushing your teeth, which is to say a habit you repeat daily that doesn't require any thought. Reduce as much friction between you and training as you can. The biggest indicators of performance of any kind is volume and consistency. Develop consistency first, then add volume. Make sure you do something on the days you don't feel like it, even if it's something small, it builds resilience, which builds consistency, which brings results. It's never too late, you're never too old and even a small step is a step forward

Sorry bit of a rant but I enjoy training and the psychology behind the motivation if it. Been training regularly in one form or another for over 25 years