It is entirely possible to be sued for accessibility violations without first being warned or provided with a cease and desist. In some cases, individuals or organizations may sue for accessibility violations without first attempting to resolve the issue through other means, such as contacting the website owner and requesting changes to be made.
It is important to note that the laws and regulations governing accessibility vary by jurisdiction, and some jurisdictions may require a specific process to be followed prior to a lawsuit being filed. For example, some jurisdictions may require that a website owner be given a specific amount of time to come into compliance with accessibility standards, or that a cease and desist letter be sent before a lawsuit can be filed.