The two most common issues with Porsche for electrical problems are the ignition switch and light switch.
Ignition controlled circuits - like the indicators and dash lights are a frequently reported issue, the problems start with intermittent behaviour but progresses to non starting, erratic malfunctions from other electrical circuits and warning lights on the dash.
The 986 is now getting long in the tooth so its reasonable to expect significant wear in these parts, You can source the ignition switch from a VAG dealer rather than go to Porsche - where you will spend 3 times as much for the same part because it comes in a Porsche logo'd box that you throw away.
If the car is not your daily drive you could remove the plastic section (the bit with all the wires the ignition barrel operates) and take it to your local VW/Audi dealer parts department who can then match it with the VW part number.
The most experienced specialist parts guys will know off the top of their head which part you need just by saying its from a 986 but nowadays the specialist parts department staff are mainly kids that can operate a computer to search for the part so they would need to see the old part.
The dash lights (not the backlights for the LCD displays) are controlled by the light switch, the most common fault that develops is failure of the dash lights, they do not come on immediately when switched on but do illuminate a few minutes later as your driving - this same circuit also powers your rear number plate lights - and when the dash lights go out so does your number plate lights - this makes it so easy to diagnose a light switch fault - and again there is a VAG part that is identical for less than half the price of the Porsche boxed part.
Inside your fusebox - on the lower section of the offside A post (to the right of the accelerator pedal) there is a fuse guide folded up and clipped to the inside of the fuse box cover - which tells you the rating and circuits protected by each individual fuse
