MaryKateW, it is a challenge to learn to play the violin with relaxed posture. Try practicing in front of the mirror a lot. Take note of any areas that look tense. See if you can mentally think through each muscle from your head to your toes, telling each of them to relax. I’d stop and do this little exercise frequently during my practice. After a couple weeks of focusing on relaxation, you will notice considerable improvement in your sound production and your playing posture.
Suzanne from Violin Tutor Pro