If you want simple, I think you either have to have a parallel "trickle" circuit as
@DThames says (either on all the time or on a switch) I've heard that some products use an
NTC Thermistor
From Wikipedia:
I don't think anything else will work in series.
If the parallel going to be automatic, you need some "signal" to control when to switch on the main low-resistance circuit. Off the top of my head, those could be:
- Time: a relay that kicks over in a set period of time, someone posted on one on this thread.
- Current: when the pre-charge path current drops to near zero, switch on the main circuit.
- Voltage: When the voltage across the pre-charge path drops to near zero, switch on the main circuit
Anything automatic is going to be have to use one of these signals, I think.