Still issues with the car not starting!

So once again I reach out to the community to answer a problem I seem to be having. I thought that I had solved the problem with my Barracuda but I guess I was wrong. About two months ago my car would intermittantly decide not to start up most often after running for a while and being hot. There would be a click when I turned the ignition to the start up position but the starter wouldn't engage. After some trouble shooting I decided to replace the rebuilt starter and solenoid with a rebuilt one and replace the starter relay on the inner fender. For a few weeks when taking the car out everything seemed fine. I thought problem solved but I was wrong. This past weekend I took the car up to the Adirondack Nationals in Lake George NY. I stopped to get a bite on the way back. Got in the car to start her up turned the key to the start position and nothing. I mean no click no sound nothing. At first I thought ok dead battery. I checked the headlights they worked fine. Took off the battery terminals cleaned them and put them back on not any better. So I took a screwdriver touched the two terminals on the starter relay and started the car up. Drove it home but I'm still not sure what the problem is? What does everyone think bad solenoid on a recently rebuilt starter or ignition switch problem? Any help would be greatly appreciated.

Carl