Google Forms are made accessible to screen readers IF a person using a screen reader turns on Google’s screen reader support. However, the form itself may have issues as describe by WebAim’s Google Forms issues.
To turn on screen reader support for Google Forms, press Control + Alt + z (on Windows) or ⌘ + Option + z (on Mac) in your form. Unless you turn off this setting, screen reader support stays on whenever you use Docs, Sheets, Slides, Forms, or Drawings on the web. Take a look at the Google support page for more information on how to edit a form with a screen reader.
Google Forms supports keyboard shortcuts as well. Open a list of shortcuts any time by pressing Ctrl + / (Windows, Chrome OS) or Command + / (Mac). Take a look at the Google support page for a complete list of the different keyboard shortcut options.
Creating an accessiible Google Form
Provide an introduction by telling your audience what the survey will be about in the description box.
Activate a progress bar by clicking the cog in the upper right corner and clicking the "Presentation" tab and selecting the "Show progress bar" option. It may also be helpful to clearly state how many questions there are in the description box.
If you have a lot of content, it is helpful to try and split it up into different sections using the "Add section" option shown here:
Make sure to incorporate the alternative text guidelines if you are using an images in your Google Form.