Look up a studio near you (avoid gimmicks like hot yoga etc. especially as a beginner), take an all levels or level 1-2 class in Vinyasa yoga, which is the typical style at least in the US. Make sure you're pushing yourself patiently but fully, make sure youre breathing deeply and not holding your breath/tensing up. Be prepared for ludicrous quantities of strange humming, possible meditation, and a sore, sore ass in the morning. I was a 160-lb varsity wrestler with a messed up back and zero flexibility. Yoga once or twice a weekend had me all Jaden Smith in no time.
This was what I was going to suggest -- make sure it's a beginning class bc they'll help you with bad alignments which aren't actually the correct stretch. I have structurally fucked up hips and knees and yoga 2x a week helped me move without pain for quite some time. i should get back into the habit of 5-6 sun salutations a morning bc that shit warms you up quick.
Do you have insight on the different yoga types? A studio near me has beginner hatha yoga on Saturdays. How does that vary from vinyasa?
Hatha yoga is all about meditation, and it includes bikram (hot) and iyengar yoga which are the most common styles besides vinyasa. Vinyasa is what is going to challenge you physically, in your muscular strength, flexibility, and balance.