the car will start after it has sat there for a couple of hours what could be the problem
When it does not start. You should check fuel pressure. The pump might be over heating that needs to cool down before it will work again.
If the pump checks out ok, I would next look at the emissions purge systems as they can cause starting problems on a lot of cars, I just can't swear if it would apply to yours because I don't know the specifics of your system. I do know that Hyundias are notorious for these problems and it is usually caused by overfilling the fuel tank that causes the parts to fail.
Looking for a Used Sable in your area?
CarGurus has 1,130 nationwide Sable listings starting at $2,150.
Search Mercury Sable Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Mercury Sable Experts