Inflatable pillow valve leaks?
Cheap pillows made in China. Throw them away. They are not fixable.
You can help it with something thick and gooey like maybe a thin coating of Vaseline or maybe hair gel. Also, are you sure you.re not over-inflating? My experience comes from air mattresses and camping. I've learned that a highly inflated "extra firm" mattress is much more likely to deflate.
You might be able to tighten the valve. There are inexpensive tools for this.