Yeah, that’s 100% how it works now, especially for Shorts and newer channels. Growth is rarely linear.
YouTube tests your video in waves. It gives you a small batch of impressions, monitors the data, and if the retention and CTR are good, it chills for a bit before pushing it to a wider wave of audience. Also, if a seed audience suddenly starts engaging with similar topics weeks later, the algorithm can easily resurrect an old, inactive video and give it a massive spike out of nowhere.