I would like to try kundalini yoga

Hi! No problem, kundalini yoga can help improve flexibility over time. Here are a few poses that may be helpful

Lotus Pose (Padmasana) - This pose develops flexibility in the hips and improves meditation postures.
Butterfly Pose (Baddha Konasana) - this pose stretches the hips and crotch and helps to open the pelvis and develop flexibility.
Child Pose (Balasana) - this pose relaxes the back, stretches the hips and shins, and helps to develop flexibility in the lower back.
Padagustasana Pose (Big Toe Pose) - this pose stretches the back of the legs and back and improves leg flexibility.
Camel Pose (Ustrasana) - this pose stretches the front of the body, chest and back and helps to develop flexibility and openness.

Remember that flexibility develops gradually, so it's important to listen to your body and not force it. I also recommend referring to https://julstory.com/kundalini-yoga-for-beginners-a-comprehensive-guide/ for more information on developing flexibility. Good luck in your kundalini yoga practice!