The nap needs somewhere to end.

A nap can be a useful pause. A nap that ends two minutes before you have to drive somewhere has left out an important part of the plan: becoming fully alert again.

Consider the coming night.

NHLBI advises adults who have trouble falling asleep at night to limit naps or take them earlier, and suggests keeping adult naps to no more than about twenty minutes. Treat that as general guidance rather than a guarantee that an alarm will make every nap refreshing.

Shift workers may have different scheduling needs. A nap around a night shift is a different decision from falling asleep on the sofa late in the evening. Work with your actual hours rather than copying someone whose day looks nothing like yours.

Allow for the waking-up part.

NIOSH describes sleep inertia: temporary grogginess and reduced performance after waking. Its duration varies and can be longer when someone is sleep deprived. Leave a buffer before driving, caring for someone in a demanding situation or doing work where an error would matter.

Choose a place where you can rest without losing track of an obligation. Set an alarm if useful, tell the person sharing responsibility with you, and make sure the plan does not depend on someone guessing you have gone to sleep.

Notice repeated, unwanted sleepiness.

If you keep falling asleep unintentionally or remain very sleepy despite allowing enough time for sleep, discuss it with a health professional. Repeatedly adding naps can hide the practical impact without explaining the cause. A useful break should leave you better able to manage the day, not continually chasing the next opportunity to lie down.