You may recite the Buddha's name sitting, standing, kneeling, or circumambulating the altar, etc. but you should not be attached to any set ways.
If you become attached to a fixed position, your body may tire easily and your mind may find it difficult to merge with the Mind of the Buddhas. To reap benefits, you should make allowances for your health or habits and skillfully select the practice that fits your circumstances.
Traditionally, Pure Land practitioners circumambulate the altar at the beginning of a Buddha Recitation session. then sit down, and, finally, kneel. However, if you feel tired when circumambulation or kneeling, you should sit down and recite. If you become drowsy while seated, you can circumambulate the altar or recite standing up, waiting for the drowsiness to go away before sitting down again. When reciting, it is better to determine the length of the session with a clock, rather than fingering a rosary, as doing so may make it difficult to focus the mind and keep it empty and pure.
~ Great Master's Yin Guang, Thirteenth Patriarch of the Pure Land school