Why am I seeing random gaps between requests?

Sometimes I will see unexplained gaps between requests like the the ones in this screenshot. In this example, there was one gap for .6 seconds & another for .8 seconds. These are pretty early in the request, so they push everything else lower, which obviously isn’t great.

What can explain these gaps? Is it just slowness on the part of the device? This test was run on here using a Galaxy S7


I’m trying to get to the bottom of a slow load time for a site. I’m currently using Chrome’s Network Waterfall visual, and I’m seeing a few long gaps between a request being fulfilled and the next one starting. I don’t know if this is something very specific to my project that I need to try and track down in the code, or if there is a general reason why this might be happening.