I've worked on three documentary projects involving dozens and dozens of portraits. It is EXTREMELY rewarding.
In my experience, few people like to have their portrait taken so a lot of the challenge of portrait projects is to make folks feel comfortable. I am not a naturally warm or outgoing person but my people skills developed incredibly. When I started, I really dreaded going up to people to ask to take their picture. Now I dive right into it with genuine pleasure. So if you feel intimidated by working with people, just be brave and dive in. Smile, shake hands, act like you are enjoying yourself. Take your time and don't be in a hurry with each person. By forcing myself not to hurry, I also minimized my technical mistakes, which I tend to commit when I get nervous.
Don't spend all your time behind the camera. On one project I walked around for two days introducing myself to people and talking to them before the actual portrait sessions. I carried a camera but did not take any pictures. That way people knew me as "the camera guy" but I could engage them personally. It made the actual shoot much more fun and relaxed.
Good luck! In my opinion any chance to shoot people and tell their story is valuable.