The only UNI-T DMM I have ever used was some years ago,& it had "sleep mode".
The trouble was,it would go to sleep in the middle of a measurement.
Apparently,it had no way of aborting this function automatically when the meter was actually doing something.
My old Fluke 77 will turn itself off if it is left unused for a reasonably long amount of time,which is useful,but these silly functions that interfere with work are a waste of time!