I can soooo relate. The number of times as a teenager I got really told off for not engaging, when in fact I had zoned out. I felt frustrated that noone knew that i was so overwhelemed i just froze and couldn't move or speak. I do remember however, focusing on one thing for a really long time, like the pattens on the tissue box, or the light switch.
Sorry, I went off track. My social worker was telling me about this just the other day. I'm not good at putting links in here. Search for 'window of tolerance' the go to images. Ok - calm down, try to explain logically.
There's a window of tolerance - when things are going ok, you are managing your coping strategies etc this is the space you are in. Here emotions can be 'tolerated and information integrated). Hyperarousal is the typical fight flight response. You are talking about hypoarousal. Where you have an absense of sensation, numbing of emotions, disable cognitive processing and reduced physical movement. It's also includes dissociation - so no suprise really that you're saying it on this forum. not sure if any info about it will help you - i have reading loads of confusing info which is why i look at hte images ...or you could try and find a video about it online, now that you know what you're looking for
How do i cope with it. Erm, I try with all my might to get to a phsically safe location. Then i sit for ages and ages (can get wet and cold if thats the weather). Like you say, theres nothing going round, no feeling etc. I usually come around to a noise that just jolts me back to reality. My social worker tells me this is where i am supposed to be using grounding techniques. Use sensory - so look at something like bright colours/flowers, smell something like baking, essential oils, touch something like leaves, a jumper, listen to something like birds or music. Honestly, i think in that state its so painful to try and do anything expect sit and do and feel nothing, that it's really hard. Sometimes, i think that your brain, like you said, is so overloaded that i's hit and off switch and will only resume when it has rested.