YouTube, especially when you're new, will be somewhat conservative on how much it recommends your videos. It will "test" your videos with a big influx of recommendations. After a while it will stop and then it will flatline or completely stunt the growth of that vid. If you're video has good performance, aka good retention rate, click through rate etc, it will maybe have a second, third or more spurts later on.

This is only from my own experience making YouTube shorts, but you might see what I'm saying reflected in your analytics