So, does he mean:
"once my car is warmed up and I try to restart it, it doesnt want to start and will run rough for a few minutes." OR...
"my car runs rough for the first few minutes till its warmed up, then it has a hard time restarting."
Seems kind of obvious to me that its the first one or he isnt communicating very well.
If he means what he wrote, when the fuel isnt moving it will pick up alot of heat from the engine compared to the fuel continually being run through the lines, through the tank, etc. So when he stops the car and goes to restart it the fuel has gotten hotter and as srbigbutt said, the fuel can boil until it has cooled off sufficiently by running through the fuel system. Thats my best guess.