ford f150 wont restart when hot

I have a 98 ford f150 4.6l. In the winter I have no problems with my truck
starting.In summer however if I "store hop" going from one store to another
short periods in between there is a chance I will come out to a truck that will
not start.I have to be starting and stopping often.At least 3 stops.Starter
sounds good.Battery has plenty of juice.Once its running it continues to
run.However,If it has this starting problem and it happens to "catch" a bit it
will ACT like vapor lock.Note I said ACT. If I let it sit and cooldown it will
eventually start and then no problems. My thoughts are its under the hood
because one time it decided to pull this stunt in the summer and it was in
beating sun right on the front hood,I also drove it a little hard(I was late and
no cops in the way,lol),and that time it did take longer to "cool down" and
start.I have driven it hard in cooler temperatures(i'm always late)and I wont
have this starting problem. It takes anywhere from 20 minutes to 50
minutes before it will start again.Please help.Im getting tired of kicking back
the seat and waiting and summers coming.I will be checking to make sure I
have a heat shield on my starter to eliminate that because if that was the
problem it would also cool faster in winter anyway.It sounds fine though.