What's the word for "swiftly lifting upper body upwards"?
The closest definition I got was from here
However, there it implies more like 'swiftly stand up from bed and go do stuff'. In my context, I'm looking more for "being in laying position, then suddenly lift upper body, while remaining in bed, changing themselves to sitting position"
Is example from above applicable for my case? Or is there another word/phrase for it?
I would suggest bolt upright
From the Oxford Living Dictionaries:
bolt upright
PHRASE
With the back very straight.
‘she sat bolt upright in bed’
The Free Dictionary gives a definition and example closer to what you're looking for:
bolt upright
verb To suddenly sit or stand up from a reclining position.
I bolted upright in bed when the phone rang in the middle of the night.