it could be worth getting checked for peti mal epilepsy, people with this simply freeze for a short period,
like I am the end explains extreme triggers can cause brain to shut off for short periods (mild dissociative motor disorder / conversion disorder)

my body (the bits that work) simply stop when i am at the end of my energy and only work after a rest, though my brain and mouth still work to some degree even when resting. I get no warning of the stop appart from the minute before hand i feel extremely tired and my muscles hurt like hxxl