Adam ignition issues

An ignition switch problem with those symptoms could point to a few things beyond just a fuse. Have you checked the starter motor relay or the ignition coil? When you turn the key, do you hear the starter motor engaging at all? It may also be worth checking the immobilizer system. Does the key turn smoothly in the ignition?

I haven't checked those other components yet. Where exactly would I locate the starter motor relay? Is it something easily accessible?

The starter motor relay location varies, but it's typically in the fuse box under the hood or near the battery. Given the intermittent nature of the problem and the rough running, I would strongly suggest that you take it to a qualified mechanic. They have the equipment to diagnose the root cause without you throwing parts at it, and will have it repaired in no time.

Thanks for the input. It turned out to be exactly as you said; the ignition switch fuse was defective. 52€ later, all is well.