Yoga has helped me tremendously. Was late to start, but glad i did. I've been at it 3 years now. I train early am and do my yoga in the evenings. Like anything else you get what you put in. YouTube has TONS of free videos. I'd recommend Yoga With Adriene as a good starting point. She has a several 30 day programs she kicks off each year with, those are beginner friendly and will help get the ball rolling mobility wise. Plus you can search her channel for any particular ailment you may have such as back pain, neck pain, ect.
Start slow and easy, 10-20 min videos to get a understanding of the art and get your body accustomed to the various poses and positions. Concentrate on breathing and listening to your body. Its a process and a humbling one at that. Yoga has kept me in the gym 6 days a week relatively pain free.
If yoga isn't your thing just try to find some form of mobility training that you can apply to your training/life and do it 6-7 days a week. Motion is the the key to staying healthy IMHO.