Any of the mantras below may be practiced at any time. However, if you want to receive maximum benefit, you should do mantra japa as a seated practice in the early morning and before you go to sleep also.
If you do japa practice every day, you will encounter every kind of condition in yourself. Some days you will feel peaceful and expansive. On other days you will feel distracted, anxious, aggravated, scared, and so on. This is normal. Just keep doing the practice. Slowly over time, these tensions will unwind. Try to relax any judgment about your condition.
Pay attention to the exact pronunciation in the recordings. You can vary the speed of your chanting.