The Alif ا without a hamza al-qat3 ء is only pronounced when one begins with that letter. In other words, if you dont begin with that Alif ا but with another letter, even if it's only one letter, you dont pronounce it. Example:
This Alif ا without a hamzat al-qat3 ء is called hamzat al-wasl.
If it were a hamzat al-qat3 it would be pronounced no matter were it is. Example:
أَنَا Ana (I/me)
وَأَنَا Wa ana