How does this play for you ? I identify as spectrum, what used to be Asperger’s, and have to work really hard to get to visual phantasia, but I can. Also worked hard to remove aural phantasia? via meditation because of negative self talk. Do you see ‘aphant’ as a useful designation? Thoughts, Ideas?
I started with medidating, deep relaxation. Laying flat works best for me. Discovered I can listen to the silence between the words. Then I was able to stretch out that silence until the words were so distant that they were mere reverberation. If there is a movie as well, that can be faded out. Later I learned a more daytime-compatible technique that is a bit hard to explain and could individually differently (opening the crown chakra).
In case it really ets your energy, and if you have access to it, consider talking to a therapist. You might be suffering from sommething like PTSD, depresseion or burn-out (in connection with autism), and those are really disorders that can be treated.
Wish you well!