1989 Mustang - starting problems

1989 - Ford Mustang V8. For the last 2 weeks I have had a problem with starting my car. I start it between 7:30 and 8:00 in the morning. Four times in the past two weeks it has not started. After about 45 minutes to an hour it will start. I have not had a lot of problems with this car before and am the original owner. I just recently had the fuel pump and battery replaced. I took it to a shop and left it there for three days and it did not have the problem. So, they could not figure it out. Any help/ info. would be great--