65 Barracuda - Idle and no start issues

Greetings early A community!

I am reaching out for help with an issue I am having trouble diagnosing (beginner here). I recently bought a 65 barracuda (273 v8) that was restored 30ish years ago. Took her out for my fist drive and ran into some problems. After about 15min of driving I hit some traffic and she died at idle. Was able to start her right up again in traffic until the car kept dying (traffic was BAD). Had to start the car up again 3 or 4 times, each time taking longer and longer to crank over until finally the starter quit. Turn the key and nothing.

Got a tow back to the garage and few days later (before trying to fix anything) tried to start her up again and to my surprise she came alive! I am curious to why this problem could have happened so it can be fixed and I can hit the road with confidence. I doubt the issue was in the fuel system since the car has a brand new carb & fuel pump. Change in temp could be a factor? Bad ground somewhere? Any help to point me in the right direction/resources would be greatly appreciated! cheers, Henry.