If it's not on an empty stomach, i'm not sure you'd really "feel" a single shot of Vodka.
Like, if i were in a situation where i'd do shots, i think it'd be hard to tell how much of what i was feeling was just "social drunkness" from having a good time in a party environment, and how much of it was the minor effect that one shot might be having.
I do believe it takes several minutes until the alcohol has been absorbed by your stomach and made it to your bloodstream.
Like, when you drink 5 shots in a row, you aren't super drunk after 20 seconds, they'll start kicking in like at least 10 minutes later.
If you wanna experiment on how long it takes to "feel" them, maybe drink at least 2 back to back and find out.