Currently, I'm working on a multitude of projects. When someone asks me what I'm writing, I have the choose a narrative and go with it.
For me, switching between different narrators isn't a struggle- usually. Other times, I can't seem to write any story. I always have ways to try and get into a character's head, though. One thing is that I'll have a genre, artist, or playlist to go with every story I'm working on. A good song with the same tone or message as your story can keep your mind on your narrative. Also, I like to act as my character would act. Part of this includes my camera- I'll take it somewhere and I'll think "How does ____ see the world around them?" and attempt to capture the picture from their point of view. Acting like my characters could also mean I decide to pretend that I'm them, or make decisions as they would. It helps me to better understand my characters.
If you have any tips on how to better understand your characters or switch between narratives, feel free to comment; I'd love to hear from you!