Good thinking Toni, usually things like this don’t happen in isolation from the family dynamics. Either in the present or in the past.
Check attention as a gain. You can then educate the parents.
For 4 year olds, conversion of hypnosis to sleep usually works like a charm.
How to do it is in the hypnosis TT manual.
Also depending on the child, also TLT works – IF the child can follow your instructions and can give you feedback that they have followed your instructions. Not all 4 year olds can do this but some can.
If so, make it like a game and fun and it’ll be fine.