Final answer:
The described symptoms are likely related to severe medical conditions affecting the nervous system, such as meningitis, sepsis, or encephalitis, that can lead to convulsions and other serious complications.
Step-by-step explanation:
The symptoms associated with violent shivering, difficulty speaking, and stiff muscles are indicative of a possible seizure or neurological infection. Severe conditions such as meningitis can present with stiff neck, confusion, and seizures along with violent shivering. Moreover, conditions leading to sepsis or encephalitis can also show similar symptoms such as high fever, chills, headaches, and restlessness, progressing to more severe outcomes including convulsions, coma, and death.