As I mentioned above, a failing coil pack or ignition system will display symptoms whilst driving. It won't just refuse to work then work all of a sudden then not work again. It will display misfires intermittently then worse as it gets more and more damaged. This is all pointing to the crank sensor as it can go for weeks without playing up then start playing up again. I've seen this many times before and had it on my car too. Change the coil pack if you wish but I would guess that it will solve nothing.