How to protect the enable signal (EN) of a car battery powered device?
There are two things I would suggest:


If it's an EN signal, it doesn't need much current to function correctly (look at the input bias current specification). Putting a large resistor in series with this pin will help.
As Tony mentioned in his comment, yes, automotive electrical systems can see huge transients as a result of load dumps. Imagine that your vehicle is driving around with your headlights on, and you then decide to turn them off. Your alternator will not respond fast enough to the sudden disappearance of that load that you'll see a huge spike in voltage on what is nominally a 12V system until it recovers. Additionally, the nature of the loads (inductive, etc.) can contribute to this.


The solution here is to find a nice TVS diode that can withstand say 100V, and protect a line around 12V nominal. It looks like that part is already designed with automotive in mind, and EN can tolerate up to 40V, so choosing a TVS diode that starts conducting around say 18V + adding a 10K series resistor should be sufficient from a protection point of view. Choosing a TVS with too low a working voltage may cause it start conducting earlier than expected, burning power / potentially destroying the device.

The other way you could do this as well would be with an optocoupler, but I don't think that is necessary here.

e: You can see here the minimum bias current:


So if we back of the envelope some margin on that (pretend it needs a minimum of 10uA), and then pretend our worst case low voltage is 10V, then a 1Mohm resistor would still allow up to 10uA of current to flow. So of course the 10K could work, or you could then use a 100K or 1M resistor in series with that input.