Do software engineers give presentations on a regular basis?
Yes. Depending on how formally you define "presentation" you will be doing it on a regular basis. You may just be explaining something to a colleague at a whiteboard, or you may be giving a more formal presentation, but in either case you still need to be able to organize your thoughts, communicate your intent and get across your message.
One of the biggest problems I see that stops developers from progressing in their careers is not lack of technical chops, but poor communication, so you should definitely spend some time trying to work on this (not to the detriment of your technical chops of course, but in addition to!)
How can I prepare myself for a presentation?
Read this blog post from Corey Foy about presenting at conferences. It's full of great links to things like the Dreyfuss Skills Acquisition Model. Understanding how people learn helps you to present and communicate ideas more effectively.
Read "Even a Geek can Speak" by Joey Asher. It's only 200 pages long and packed full of great advice about how to get your point across.
Would I get less nervous if I gave more presentations?
Yes. We do weekly "brown bag" lunch sessions at work. They started off with some of the more senior people teaching the more junior, but we now use them to get people on the team, regardless of seniority, to present to one another about anything that's interesting to them: a blog post they've read; some code they're working on; a tech book they're reading. It really doesn't matter what: the purpose is to get people used to standing up in front of a room full of people and presenting. We don't allow prep time (we choose the person that morning) and we frown upon any powerpoints or formal presentations. I've noticed the general communication in the office and level of comfort of the team in communicating their ideas has improved immensely.
On a personal level, I was a technical trainer for a while and the first few times I delivered the classes I was almost physically sick with nerves beforehand. Now, many years and many presentations later I'm pretty comfortable speaking in front of groups of any size and I think I can communicate fairly well. There's definitely nothing special about me in this regard, so if you practice presentation skills and do a small amount of research about how people learn, you will be fine.