When a cat is very relaxed, the relaxation of its jaw will cause its tongue to stick out slightly.
Sticking out its tongue while grooming itself...
It's normal, but it will only happen briefly.
The cat was suddenly interrupted while grooming itself, its attention was diverted, and its tongue hadn't had time to retract.
Sometimes I can't close my mouth, and I stick out my tongue slightly...

This may happen occasionally in cats with smaller jawbones.
Some breeds of cats (often due to unregulated breeding resulting in congenital deformities) have smaller jawbones and cannot close their mouths properly, sometimes leaving their tongues slightly sticking out.
He was panting heavily as he stuck out his tongue...
This is unusual! This indicates that the cat is having difficulty breathing; you should intervene as soon as possible!
Priority should be given to conditions such as heart disease (heart failure or pleural effusion), heatstroke, and motion sickness.
Important note: Unlike dogs, cats sticking out their tongues is not due to heat, but rather to difficulty breathing; if it worsens, it can lead to breathing difficulties, insufficient oxygen supply, and even shock or sudden death.
Therefore, when playing with your cat, don't let it play wildly until it sticks out its tongue; if your cat often sticks out its tongue after playing for a few minutes (exercise intolerance), it should also be checked for heart disease.
When sticking out your tongue, you drool...
Something's wrong!
Priority should be given to cases involving oral diseases, poisoning, or foreign bodies in the mouth.

When cats have oral diseases, the inflammation is accompanied by pain. In addition to drooling, they may also eat less, be unable to close their mouths, and have bad breath.
When poisoned, cats will drool excessively and may experience symptoms such as vomiting, difficulty breathing, and dizziness.
When a cat has a foreign object in its mouth, it will try to swallow and stick out its tongue to remove the small object stuck in its mouth.