Peugeot 106 Starting Issue

Could be a voltage drop somewhere, or even the ignition switch. Have you checked the battery condition? A heavily discharged battery can cause all sorts of weird electrical problems. Is the power supply stable?

Battery seems ok, but I'll double check. Where exactly should I be looking for a voltage drop? Any specific areas known to cause issues on the 106?

Given the age, a short circuit could be the culprit. And without proper diagnostic tools, it is hard to pinpoint. If battery checks out, and you're not confident tracing the wiring, best bet is a workshop. They can properly test the electrical system.

Thanks for the help, took it to a shop, and as you suggested, the battery was defective. 290€ later and it's sorted.