On the 737, it is the result of the mach trim system action after take off when the aircraft is in the FCNSE region.(within 10 secs after lift off).
The elevators will move to a neutral shift position and will allow the aircraft to have a larger nose up attitude for a specific reason.
This neutral shift is felt by you as a 'pause'...
You can pitch up through this 'pause' for the loss of a few knots...
The third answer is that the "pause" is designed into these aircraft to minimise tail strike if the rotation is too fast?
No,proper training and reading/applying FCTM do.
The elevator neutral shift is to allow a higher attitude in case of engine failure.