Having an issue with review times

It’s not random, these are the SRS times for items:

SRS Level Next Level Total Wait Review
Apprentice 1 4h - Lesson
Apprentice 2 8h 4h 1
Apprentice 3 ~1d 12h 2
Apprentice 4 ~2d 1d 11h 3
Guru 1 ~1w 3d 10h 4
Guru 2 ~2w 1w 3d 9h 5
Master ~1M 3w 3d 8h 6
Enlightened ~4M 7w 5d 7h 7
Burned - 24w 6d 6h 8

So depending on the time of day you do lessons/reviews, the srs level that the items are at (ex apprentice items will show up more frequently), the # of items you get correct vs incorrect, etc, will all determine the timeline of your upcoming reviews

Maybe installing the Ultimate Timeline script will help you visualize what to expect ^^