Once in a while your site may be loading too slow. Or slower than you’d like to.
Anyway, its speed can be improved.
Try to optimize your images for web (for example: set your portfolio images to 960x670px size) and use smaller images (in case it’s not full screen background or so). You really don’t need full hd resolution image for team member photo – it’ll be scaled to fit the element, and any time the page is reloaded, the site will need to reload it. Generally images shouldn’t be greater than 2000px in width. For additional image compression you can use services like tinypng, or programs like Adobe Photoshop or GIMP.
The best way is to use caching plugins, like W3 Total Cache or WP Super Cache. They really help to increase the site loading speed, because the site will be cached and a copy will be pulled from the cache instead of reloading every element over on reload. If you want some premium plugin we can recommended you WP Rocket.