An increasingly common bottleneck at the back of the fuse panel, a few unplugs/replugs and wiggling can go a long way!
-explanation- Corrosion increases resistance on the incoming battery connection. The starter solenoid's current path is impeded and it's operation impaired, resulting in slow actuation. The slow actuation in turn causes poor switch contact for the starter motor itself, which in turn impedes it's current path. It also builds up carbon deposits on the switch contacts that slowly make the situation worse. After freshening up these contacts, repeated actuation of the starter solenoid at proper speeds can remove some of the build up and it can start to function better after consecutive cranks.
