It's odd that razor sharp teeth is kind of the gold standard for a scary animal, but honestly, getting swallowed whole and slowly digested by stomach acid sounds so much more horrific. I'd so much rather a T-Rex eat me than that.
Probably not enough volume to engulf you and make you drown. Usually stomach acid is strong enough to irritate but not dissolve a whole prey, so those two are out. However accidental inhalation and fumes might be a motherfucker and getting it into the eyes would be horrendous.
Two possible scenarios:
Suffocation due to a lack of oxygen.
Crushed to death by the stomach. It is conceivable that this baby (slaps roof of the dinosaur) can crush large prey to death in the stomach and grind it to small bits by having an especially strong muscle lining.
I recall reading a meme about the ocean being bullshit, something along the lines of "the most common way to die on land is something making your blood fall out".
The stomach isn't like a big cave with a pool af acid in it. It is compacted by muscles around it so if you are swallowed whole, you would have to fight against those muscles to even be able to move at all. If your arms are above your head it's likely you would die before you are able to move them to your hips to draw your knives. If they are at your hips, good look moving the knives to point outwards. Also the stomache is lined with thick mucous to protect it from sharp objects...
Also it's completely dark and disorienting.
It's almost certainly you'd drown, suffocate and get crushed VERY quickly after getting swallowed alive.
You can blame the Magic School Bus for my incorrect perception of how the stomach works. I know they cleared things up at the end, but as a kid I remembered only the adventures.
The stomach isn't like a big cave with a pool af acid in it.
Unless your predator has been eating a lot of air or drinking a lot of soda/beer. Although one burp would quickly get rid of all that headroom. And the CO2 from carbonation would quickly suffocate you as well as it's heavier than air.