To suggest that God could come from somewhere is to imply that there is a place where He resides after having come from somewhere else. He doesn’t reside in a place exterior to Himself. All places reside in Him. He has no beginning since He always existed and always will.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.