Responsive Movement

I have a responsive site and I’ve notice that my site: https://therockofsouthwest.com/ more so jumps to different sizes as you resize your browser. Unlike a site like this one: https://www.grahamrobertsonmiller.co.uk/ where the resizing is a slow steady pace. Why is this? I don’t want my site to jump sizes.

I am using a theme called Caffeine by the Muffin Group so maybe that’s the issue but just in case is was something easy I thought I would ask. Also to be honest, I don’t know much about website design either.