Grey screen solved / No internet Splash screen

Hope this is the right place. I had an issue with my 2013 IMac and also my 2016 Macbook. Both slightly different issues.

The Imac would give me a grey screen on start up say after a long shut down overnight for example and also the Mac would not see my mouse for an age sometimes up to 2 mins or more. All would eventually spring to life after about 1-2 mins of waiting

The Macbook what not such an issue. I always leave it on unless I am going away and def not using it. So the issue was when I lift the screen the up and the MacBook comes on as normal but I have a splash screen on which says no internet immediately on start? Weird, anyway no issues I just acknowledged it and carried on as normal no issues.

Ok so where is this going, well both issues were solved by turning off the desert screen saver with Mojave and where the picture changes through the day getting darker with night etc dynamic I think. Both issues disappeared immediately 1 month later neither issue has come back.

so if any one else has the same issues as me try that, it works...