This sudden onset unilateral weakness is likely a stroke and "time is brain" in these situations - if given within 4 hours, thrombolysis can lead to total recovery.
History, examination, bloods (and adequate IV access) and ECG are important measures and a non-contrast CT scan is the first-line investigation to perform.
Presentation
Acute right sided weakness. Presented to ED within 2 hours of the onset of weakness.