You are not being “suffocated” in the sense that you aren’t allowed to breathe. I suggest you do some looking around and check out events where people have entered spaces that can have no/limited oxygen such as mines or anchor chain lockers on ships. They often simply drop unconscious and are dead fairly quickly. The victim isn’t re-breathing CO2, which is what gives us that panicked lack of air feeling, or someone holding something over your face making it difficult to breathe.

If you’ve ever had a medical procedure that puts you under, I can assure you there’s nothing remembered to be aware of.