What is chief is the relationship, yes… but what are you saying about your relationship with your posture?
Does Jesus care if you come to Church in slippers and pyjamas? He cares about the relationship. But what are you saying when you treat your Lord so flippantly as to dress like that?
If you can’t kneel, you can sit straight up. I’ve prayed it once while on a walk in a place where I would not be distracted. Do not lie down unless you are bedridden. Mary in Heaven is far beyond us and is constantly praying for us, even when you forget about her and go about your daily business. And when you come back to her, you had better show her all the respect you would show your own mother, and more!
In my opinion, please do not pray it while driving, because you have a duty to others on the road and a duty to Mary, and the two will conflict.
Read Saint Louis de Montfort’s
Secret of the Rosary (here’s a quick link)
montfort.org/content/uploads/pdf/PDF_EN_29_1.pdf
I would draw your attention to section 128, 129, and 143
Edited to correct sections