It really is sheer hell trying to start a new novel - or any writing project - and I know, because here I am, starting my second novel!
But I had a fit of inspiration about that dreaded FIRST SENTENCE - you know the one, the all-important, do-or-die, grab 'em by the throat quick or lose them forever first line that keeps us writers up at night, and that we spend days, weeks or longer obsessing over and waiting for lightning to strike. It sets the tone, and the reader's expectations, for the whole novel. It should encapsulate the journey, the arc. And it's the first thing a potential agent or publisher will see, that makes them either sit up and take notice, or just skim a few pages and issue a form rejection. (Goddess bless agents who even bother to let you know it's a No.)
So here's a little tip as you ponder and fret, putting off starting that next project while you think about striking just the right first note:
DON'T.
Do not write the first sentence of your new project first. No matter what you write, you're going to rewrite and revise anyway, so don't give any thought at all to your first sentence until you are well into your first rewrite/revision. You won't really have the whole flavor and feel for the project until after you've finished the first draft.
My advice is to start writing scenes you know are going near the beginning of the story, a whole bunch of them - actions you've thought might make a good starting point, conversations between characters that set up the conflict, descriptions of people, places, events you already know are going right there up front, just not exactly which one will be the first scene. Try to make some of those scenes pit a couple of people against each other - Oooo, they hate each other! Give them something to fight about, turn up the tension and the conflict two notches, or even three. Burn some bridges, why not? (Or don't - it's literary fiction, it's modernist, it's an experiment, hooray! BUILD a bridge, make love, IDGAF.)
As you write out these scenes, and your plot thickens, and you're off to the races with the rest of the story, those beginning scenes will be simmering away while you work. When you come back to them later, one of them is going to be the clear winner; one of them is going to have a line dancing in its seat with its hand flapping in the air: Me! Pick me! Oh, me! Please! I'm your first line! YES!