1989 Honda Prelude Cranks over but won't start after being

I drive the car somewhere, park and leave it usually in hot weather. I come back and the car will crank over but not start.
Plenty of fuel, battery good.
Then I leave it until the afternoon and it's cooled down and it starts first go.

Mechanic has suggested sending the computer away to be checked. Of course this will be expensive and still no guarantees.

Any suggestions?