You seem to be very concerned about this w/ words like ‘disturbs’ & ‘deathly calm.’ You can explore these feelings & states w/o any concern for your safety as in harming your self, physically or nonphysically. It is very common for new energetic experiences to be unsettling, even when we've been trying to have them. As you continue do these you'll find the effects become something that is expected & they lose the uncertainty that often fuels fear about them.
I doubt you will pass out, but use common sense & if you feel excessively woozy, sit or lay down. Or do the meditation exercise already seated so if you passed out you wouldn’t fall. Many experienced meditation masters have learned to slow down their pulse rate significantly when meditating.
Worrying about the What Ifs will keep you at a fairly low frequency, preventing you from exploring, so actively move past these fears
. Our life force is VERY firmly connected to our physical body, so don’t worry about exploring unfamiliar situations. For millennia millions around the world have meditated, exploring the same territory, & found it to be a rewarding experience. Have fun w/ it.
Give your self credit for reaching out to find some answers about something that is unsettling to you. This is an empowered step to seek information instead is just staying fearful.