fiction - How to avoid repetitive sentence structure?

I've realized that I always start sentences with (name of character), he, she, it, they, her, his, the, after (a moment/that), and then. I wonder if there's any useful exercise or tip to reduce this?

A sample of my writing:

Adele wondered where was everyone. It occurred to her that maybe they were in a safe place now. Maybe everyone knew about this, and I was the only one who didn’t, she thought. She stared at her hands, and thought about the things that had actually belonged to her in this world. She realized that nothing really had. All the material things she’d ever owned had turned into dust. Boys had possessed her, but they’d never been hers. Her friends had just been people who had accompanied her throughout her life. Adele sat down, and looked back to the moon. She’d been left alone in the world, waiting for the moon to fall from the sky.

Answer

Even though you notice the problem in the first words (in the subjects of the sentences), I think the problem is elsewhere: Each of the first five sentences has a verb that reminds that we're in Adele's head. But we already know we're in Adele's head, so these reminders are unnecessary, and they weaken the sentences.

Consider this edit, which removes all five reminders:

Adele wondered where was everyone. Maybe they were in a safe place now. Maybe everyone knew about this, and she was the only one who didn’t. She stared at her hands. What had actually belonged to her in this world? Nothing really had. All the material things she’d ever owned had turned into dust. Boys had possessed her, but they’d never been hers. Her friends had just been people who had accompanied her throughout her life. Adele sat down, and looked back to the moon. She’d been left alone in the world, waiting for the moon to fall from the sky.

I think this is an improvement, though it is perhaps too relentlessly staccato now.

If you want to explore the dangers and delights of sentence structures, try this exercise.

1. Pick a scene you've already written, about 500 words long.


2. Rewrite the entire scene using sentences no longer than 10 words. If this is too easy, try sentences no longer than 7 words.



3. Rewrite the original scene using sentences no shorter than 25 words (or 35 if 25 is too easy).


4. Read each version aloud.


5. 
   

   Make notes about:

   
   
   
   
   • the effects of sentence length
   
   
   • what different sentence structures you used
   
   
   • the effects of different sentence structures
   
   
   • the rhythms created by different lengths and structures
   
   
   • which effects you liked and which you disliked
   
   
   
   • anything else you notice
   
   
   
   


6. Rewrite the original scene, using everything you've learned about the effects sentence length.