I would say it definitely sounds like it's flooding after you shut it off.
A high float level (and/or bad needle and seat) will allow fuel to drip from the boosters once the engine is shut off. (It will typically cause a rich idle as well)..
This will make it seem like it's flooded when you try to restart it.....IE have to put it to the floor for it to crank.
That's where I would start.
Vapor lock won't cause your issue.....Trouble restarting.
Just because the fuel boils in the fuel line once it's shut off doesn't mean there still isn't fuel in the bowls.
The fuel in the bowls alone is enough to start it and run it for a few seconds.
The next thing I would check for is a bad power valve of metering block gasket.