I can so relate to this! I am pretty laid back to begin with and I really struggled so bad with this. I made daily a vlog entry's for about 2 weeks straight. On the third week provided I had a general plan I felt much less stiff, and it showed on the camera too. Generally just doing it for a long time makes it feel more normal, which leads to more natural on screen presents. I still have a LONG way to go, but 3 weeks made a huge difference, si i figure another month it will be old hat. Good Luck with your channel!