THis is exactly the thing I have the most problem with. Do start a sentence with a vowel is next to impossible. If i try, I cant get a sound out and if I try to force it my mouth just contracts and expands rapidly. What I do is I have small methods for making things easier in the day to day-living. Like another one already said, tricking your brain into making two words into one. So, if I wanted to start a sentence with "If I want to do that..." I change it to "...n-If i want to do that..." like I said the word "and" under my breath but shortening it so it becomes "n-If" etcetera. Or adding a "Well..." before the name that start with a vowel or "But..." before the name or whatever. Hope it helps somewhat.