Can anyone offer advice on how to start writing a first novel after coming up with an idea but feeling unsure of where to begin?

I know I'm in the minority on this question, but as not all writers work the same way the way I write might work for you where it won't for others.

So you have a story idea, great! Now start writing about it. You probably have an idea for a main character so take that person and start writing their story exactly as it comes to you. Don't always worry about exactly where it is going, not at first. Write on it until you get a firm feeling for the characters and the world they inhabit. Once you do, if this kind of writing is for you, then you will find that the characters themselves will actually seem to take over the story as if they are writing it instead of you. I can't tell you how many times I planned something in my writing beforehand then when I went to write out the scene it went a totally different way and ended up much better for it. This is often known as pantsing, or writing by the seat of your pants.

Once you have the whole story out of you and on the page, then go back and revise. Fill out some details, add some scenes, maybe redo the beginning now that you know the characters better, or start the story at a different point and work in those initial establishing details you put in the beginning as a more integrated part of the story.

By no means does this writing style work for everyone. Then again, plotting everything out in advance doesn't work for everyone either.

There is also the combination method between the two where you make a list of major plot points you want to hit and in roughly what order. Then you start to write based on them. Almost like a timeline.

No matter which way you go, the important part is to somehow get that story inside of you out and into the world. So if plotting is keeping you from doing that then try another method, even if it’s only for the beginning to get you started.

Good luck and happy writing.