'91 Passat - P/N Switch or Relay? HELP!

Sometimes, in an intermittent fashion, I turn the key over and --- nothing (except the fuel pump noise) It doesn't seem to have a correlation to hot/cold or wiggling the key, etc.

I can leave the key "on":

and jumper a wire or screwdriver from the solenoid to the post on the starter -- a common method -- starts no problem (replaced the starter anyways so it's new) :)

I DON'T want another god-damn mickey-mouse "fix" like a momentary switch in the dash, if I can at all help it. Somebody already "fixed" my 02 sensor wiring in such fashion, causing it to fail an emissions test twice as I detailed in another thread. This car is otherwise MINT, esp. engine and interior, and I've corrected three other exhaust mickey-mouse "fixes" done by a previous owner/mechanic who didn't give a damn and was too f&*%$ing LAZY to do the job right, the first time.

After much searching and Googling to death, I have come to the conclusion(s) that: it's either related to the park/neutral switch or the relay to which it's attached or the associated wiring between them and the transmission control unit under the back seat.

In a 91 16V auto sedan Wolfsburg production March 1990, where the heck is the relay and the switch located??? Part numbers to ask for???
on this beast, I've only had it 2 weeks and I'm discovering more foibles on this sucker every DAY... !!! I want to get it on the ROAD, and out of the shop!

Much appreciated...thanks...AGAIN! :-)

Starter interlock relay is in position #20, that's the very top row of add-on relays, second from left. The switch is part of the multi-function switch on the transmission right above the shift linkage.

Thanks...I'll be checking them out over the next week...