Set your Instant Pot to the 'Sauté' mode. Once hot, add olive oil and let it heat up.
Add the diced onion, sliced carrots, and celery to the pot. Sauté for about 5 minutes until the vegetables begin to soften.
Stir in the minced garlic and sauté for another minute until fragrant.
Add the boneless chicken breasts to the pot. Pour in the chicken broth, and add thyme, parsley, and black pepper. Stir to combine.
Close the lid of the Instant Pot, ensuring the valve is set to 'Sealing'. Cook on 'High Pressure' for 10 minutes.
After cooking, allow the pressure to release naturally for 5 minutes, then carefully switch the valve to 'Venting' to release the remaining pressure.
Remove the chicken from the pot and shred it using two forks. Return the shredded chicken to the pot.
Set the Instant Pot back to 'Sauté' mode, and add the egg noodles. Cook for 6-8 minutes, or until the noodles are tender, following package instructions.
If using spinach, stir it in just before serving, allowing it to wilt.
Taste the soup and adjust the seasoning with salt if needed. Serve hot.