I have a Trane gas furnace with a separate central air conditioning unit that is 9 years old.
When using my central a/c, I find that the blower fan shuts off after 4-8 hrs of use. After waiting several hours you can turn it back on and it works just fine for another 4-8 hrs.

Is something overheating? I know that the garage gets hot but it has shut off when the garage wasn't that hot either. The control board was changed about 5 years ago (under warranty) after shorting out. I checked the LED diag red light, and I get a slow continuous blink, which indicates no error. Anything else I should check?

Thank you kindly, Valarie

It seems the capacitor for the blower motor might be defective or it could be the blower motor itself going off on the internal overload. I would just replace the capacitor first since you probably do not have a dedicated capacitor tester. If the capacitor does not do the trick post back. NOTE use the like same capacitor for a replacement.

Could not have said it better myself... do what hcac1000 says.