What prevents people from sneezing in their sleep?

The nerve that triggers a sneeze is asleep or partially paralyzed during sleep, especially during REM sleep. People also can not feel tickles or other major sensations while in REM sleep. It is possible to sneeze when in light sleep like right before waking up or before deep sleep sets in. Scientists are still trying to figure out exactly how it all works but it seems to be connected to the brainstem.

https://www.healthline.com/health/can-you-sneeze-in-your-sleep#how-sleep-affects-sneezing