Dear yoga enthusiast, congrats on your new yoga schedule, I think you are doing right and still you can continue with the same pranayama practice. However, still I would like to know as to how do you practice the anulom-vilom pranayama - mudra of your hands, your thoughts during your practice, your age/ gender, etc. so as to enable me to suggest you with clarity.
I presume that the vibrations may be due to fatigue of muscles in the lower limbs for continuously stretched sukhasana posture for 15-20 minutes. Kundalini awakening requires sadhana, purification of diet, purification of thoughts, purification of body, etc. which gives glimpses as soon as most of the naadis become purified through pranayamas.
In the first instance, I may suggest you to practice pranayama after ensuring that you are relaxed and not tired out of the chaotic work/ engagements of the whole day. Pranayama in the early stages be practiced without retention of breath as well as with fully harmony and relaxed mind. When breathe in and out, do it slowly and you should be fully aware of your breathe. Breathe like your are drinking the air through nostrils, such should be your awareness and then you will enjoy the pranayama. Spine be straight.
I hope that I have been able to reply your query with your full satisfaction in the first instance. I expect your follow-up to allow me to suggest precisely.