it happens to me every time. i think you'll be fine.
examples:

- i'll be laying down in bed with my eyes shut and i feel like im sinking through the bed and that i dont really exist and i get really scared and i start to shake.

- i'll be crossing a busy road at a light and i will get like halfway across and get so scared that i might get hit by a car that i stop in the middle of the road and i just cant move and start shaking.

- i'll be just sitting down and i'll start to think that maby i am really dead and just imagining all of it. and im really not real. i get so scared thinking that i really dont exist so i just sit there shaking in the middle of class.