What would be causing your 1974 Super Beetle to not turn over with a few turns of the key yet sometimes starts right off?

it may be your alternator going bad that is what happened to mine, and i just changed the alternator, and it fires right up, to check your alternator start your car if it will start, and while its running take off your positive battery cable, if it dies your alternator is bad if it stays runnign your alternator is good, then it could just be your compression, or something in your gas.