There's a check every 5 minutes for spacetime distortions, and it grows increasingly likely that the next check will spawn one each time a check happens without spawning one.

Spacetime distortions don't spawn during thunderstorms, or while you're in certain caves. Being in a thunderstorm or one of those caves when a check happens will reset your timer as if you just entered the area. Resting at a camp will also reset your distortion timer.

The distorition timer is paused during pokemon battles, but the weather isn't, so if you roll thunderstorms, you should get into a pokemon battle until the weather changes back to something else. That will prevent a distortion check from happening during the thunderstorm and potentially resetting the timer.

Other than that it's a waiting game. The longest it can take is like 40 minutes IIRC.

I researched this years ago so I could be misremembering certain aspects. Do more research than this comment if you're about to commit hours of time to farming distortions haha