What does it when when one start experiencing pulse in the implanted areas on a Hair transplant?

If you have throbbing on your transplanted area, it is not normal.  You should contact your doctor for a follow up.

Throbbing is generally not a common symptom to have, especially if it develops later on and not immediately after the surgery. Having it in a specific area is also a cause for concern as opposed to simply feeling it over the entire scalp. Regardless, contact your doctor about it, since its possible it's nothing but also possible there is some complication.

You should return to see your doctor of there is throbbing in one particular place. If it is general scalp throbbing, I would not worry about it.

This could possibly be due to an arteriovenous fistula, which is an abnormal connection that can form between an artery and a vein during the first 2-3 weeks after surgery. You should notify your surgeon about this, as you may require further surgery.