i have ptsd.. i have repressed memories from combat. i cant remember many crucial times during my tours in the USMC.

that said i get the jolting feeling as well. sometimes i feel like i just fell asleep literally seconds before it happens.
i take zoloft and other VA prescribed medications. i do not drink at all.

i have no clue what it is; cant even speculate. but OP did you have time overseas in combat?