Each regeneration occurs because of something, like radiation poisoning from the 3rd to the 4th and 10th to the 11th ... or old age as to 11 to new cycle.
But, what are the causes of his "death" ? What are the reasons behind each regeneration?
If I understand what you are asking, this Doctor Who Wiki page will answer your question.
The relevant bit here:
1 -11th Doctor's details added by me; not listed on the linked page.