2002 Ford Taurus Starting

My Taurus about a month ago began to have trouble starting. Sometimes it starts right up and sometimes it does nothing, not even turn over. One night we spent an hour trying to start it and it finally turned over. We took it to a repair shop the next day and of course it never hesitated or showed a problem for them and they kept it all day. Sometimes even if it doesn't turn over if you keep trying and you hold the ignition over in the start postiion for a minute or two it will begin to make a turning over sound until it finally starts. The battery works and everything plays with no problem. Please help, Thanks