Somotogravic Illusions can and will occur throughout all pilots' aviation careers when flight operations include instrument flight conditions, low vis operations and/or night flying.
The basic reason for this is that the human vestibular and other balance system sensors are not naturally trained for flight accelerations (we are not birds!).
Somogravic illusions can can result from gentle (and therefore imperceptible), medium or rapid accelerations, or attitude change in any of the 3 axis.
The vestibular sense organ is UNABLE to resolve the difference between an acceleration or attitude change without the input from some other sense organ.
Slow bank angle change, for example (less than about one degree per second), cannot even be perceived the vestibular system.
I thought that this reference and associated included references was interesting:
https://skybrary.aero/helicopter-som...usions-skyclip
And the Wiki coverage is comprehensive:
https://en.wikipedia.org/wiki/Sensor...ns_in_aviation