Performance drops drastically after ~30 seconds from boot

[wop55]

The test program I run from inside bash:

• time sleep 5

5.010 seconds is the output before the slowdown begins.
after around 30 seconds, the same command can take 8, 14, 10.. seconds
it even seems that running for loop test programs, is 5x slower after the performance dropdown within ~30 seconds from boot.

[raspiduino]

Can you try it on a different machine? Maybe it's just your?

[wop55]

Can you try it on a different machine? Maybe it's just your?

I tried to run it on 3 MacBooks, it behaves the same.