I have a really powerful PC, so it's definitely not slow Hardware, and I never had this issue before as the launcher used to boot instantly.

My issue is that whenever I open up the Minecraft Launcher, it takes about 7 seconds to load, when before the issue there was no delay whatsoever, but when it eventually does load, it says I'm not connected to the internet for another 5 seconds, and then suddenly switches to saying I am (I have an uninterrupted, solid connection to the internet and am connected the whole time it says I am not). After clicking play, Minecraft itself loads instantly and runs completely fine.

I have repaired the launcher using the installer, and reinstalled the entire launcher when that didn't work and still nothing changes. I am using Optifine, but this issue didn't start after I installed Optifine I don't think. 

One thing I noticed was that when I unplugged my Ethernet cable it booted instantly, and still boots instantly when I am not connected to the internet, and it still has this issue when I use a Wi-Fi Card, so its not a dodgy ethernet cable etc. The only thing I can think is it's something to do with connecting to a server, but my Wi-Fi/Ethernet is 24Mbps, so I don't have slow Ethernet either, and I don't know why this would sudddenly happen, as it was fine before.

I don't know what could have caused this, and I know it's not the end of the world, but I just find it frustrating taking so long to load when it should be loading instantly like it did before. There have been many updates to the launcher since this issue and none have changed this issue.