1974 Volkswagen Beetle coil over heat

When I start the car it runs and idles great once I drive about4 to 6 miles the car starts to sputter and spit in fourth gear I shift down and have petal to the floor only runs at 50 mph for maybe a mile the car shuts off and won't start acts like its out of gas. Once it set for 20/30 mins it fires up and the process starts all over again. Replaced plugs distributor cap button wires and coil. Also traced the wire to coil no shorts found. Ne idea what might cause coil to heat up to cause car to not run