Atos Poor Starting

Sounds familiar! I had a similar problem with my old Opel Corsa a few years back. Hard starting, voltage seemed okay at first glance, but it was a sneaky voltage drop somewhere. Have you checked for voltage drops across the starter motor while cranking? Also, wiggle the wiring harness a bit while someone tries to start it - might be a short circuit somewhere.

Voltage drop across the starter motor, huh? I haven't tried that specifically. Where exactly should I be probing with the multimeter? And which part of the wiring harness are you suggesting I wiggle?

Yeah, clip one multimeter lead to the battery positive terminal and the other to the starter motor positive terminal while someone cranks the engine. You shouldn't see more than about 0.5V drop. As for the wiring harness, focus on the sections near the starter motor, ignition switch, and any points where the harness might rub against the chassis. Honestly, though, intermittent electrical issues can be a pain to diagnose. If you're not comfortable digging too deep, a workshop with proper diagnostic tools might be your best bet.

Thanks a lot for the advice! I did as you suggested, and it seems I need to go to the workshop as you mentioned. It turned out to be a defective battery, heavily discharged, after a short circuit in the wiring harness. Cost me 290€ to get it sorted out. Appreciate the help!