E-commerce Site Error Fix Node.JS

I have encountered a "Start Error" on my e-commerce website dedicated to selling goods. This issue arose today, and no prior changes were made to the site, such as plugin installations or updates.

Requirements:
- Diagnose and resolve the "Start Error" promptly
- Check the error via the 'npm start' command
- Ensure the website is fully functional post-fix
- Provide a brief report on the cause of the error and preventative measures

Ideal Skills:
- Expertise in troubleshooting e-commerce site errors
- Strong knowledge of website backend and server issues
- Experience with no-change related errors

Looking for a professional with a proven track record in resolving similar errors quickly and efficiently.