Ease into it. When CrossFit started catching on, a lot of beginners started going full out and got rhabdomyolysis.
Not a good goal for health and fitness.
To be fair, the routines were too hard and too long.
https://nypost.com/2017/04/07/deadly-condition-linked-to-crossfit-on-the-rise/
Yep, I probably can go at about 80-90% for 15 second stretches, but my rest periods are still too long, and I stretch the whole workout to 30 minutes.