How did the childhood experiences of Siddhartha Gautama lead to his questioning of the spiritual practices of his time

Answer 1

We don't know. Accounts of his life were written many years after he died by people who idolized him. However, this article sums up what many think influenced him.

http://encarta.msn.com/encyclopedia_761552413/Buddha.html

Answer 2

Here's another -- again, as Ms. Sue said, not very detailed about certain parts of his life:

http://www.wsu.edu/~dee/BUDDHISM/SIDD.HTM