Catatonia + Autism
Information on catatonia and catatonia-like states for autistic individuals, who are more likely to suffer from an intermittent form of catatonia than one that is acute.
Some general information on How to Spot and Treat Catatonia (PDF) that does mention Autism.
Here are powerpoint slides and here is a link to Dr. Ruth Aspy presenting Catatonia and ASD: Hidden in Plain Sight, Part one video. Here is a link to part two slides where Dr. Barry Grossman speaks to the waxing and waning nature of the condition, Part Two video.
Dr. Shah is at the forefront of identifying catatonia-like individuals and wrote a book to describe cases and her approach, which involves assessing an individual's life for triggers that induce slowed responses and reducing as much stress as possible. Here is a link to her book and below is a youtube video of 4 minutes run time of Dr. Shah explaining.
Post covid catatonia is also possible
These are UK based guides. One is for Autistic adults experiencing catatonia. Another is for carers and parents. And another is for professionals. These are not as thorough or ideal as Shah or other source material I have found but there is dearth of material for catatonic Autistic people.