1992 BMW 735 won't start after it sits for an hour

I have to turn it over 8+ times to get it to start after it sits for more than an hour after running. Usually starts right up in the morning and within 15 minutes after turning off. But if it sits for more than an hour it acts like it doesn't get fuel. Replaced fuel pump and fuel pressure regulator. Could it be a relay?? Any ideas would be appreciated. - Annie :)