Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Get emergency help after a road crash, serious fall, significant head injury, or near-drowning.
New one-sided weakness, trouble speaking, chest pain, severe breathing difficulty, or loss of consciousness should also be treated as an emergency rather than assumed to be narcolepsy or cataplexy.
Seek prompt medical advice if sleep attacks occur while driving, cooking, swimming, working at height, or operating machinery.
Stop the unsafe activity until the risk has been assessed.
Arrange a routine medical appointment if you regularly struggle to stay awake during the day despite allowing enough time for sleep.
Also seek assessment for episodes of emotion-triggered weakness, repeated sleep paralysis, vivid experiences around sleep, or sleepiness that affects work, school, or relationships.
The article also says
A typical cataplexy episode preserves awareness and resolves quickly.
A first episode, an unusual prolonged episode, or weakness without an emotional trigger should be medically assessed because other conditions can look similar.
Every sign above is quoted from the sofidex article on Narcolepsy. If you are not sure, err upward — it is always reasonable to be checked.