Just start writing, don't overthink it. Sometimes the hardest part is getting those first words down.
First, clear your mind and create a quiet, distraction-free space. Then, make a rough outline of where you want the story to go next. It can also help to talk to other writers or join a writing group for motivation and feedback.
Well, you could try re-reading what you've written before to get back into the story. Also, set a small daily writing goal to build momentum. Maybe think about what inspired you to start the novel in the first place and use that to reignite your passion.