I had a reflash and no issues since (fingers crossed).

UPDATE: It was the memory function tied to the key and person seat memory buttons. I have the sport seats, so PCM settings are also saved. I (or the detailer) had hit a button that had not been set yet, so it loaded default factory settings only. This cleared all my current settings, giving the impression of a reboot.


Thinking now that it might be fine and the culprit is the memory function. According to the manual, if the memory seat funtion is on, the settings, including PCM, are saved to the key at locking. If it is off, no settings are saved. I had the car detailed yesterday, had the problem right after. Perhaps he turned the memory off, locked the car then unlocked it. That could clear the settings. As the PCM was set on iPod, I didn't notice anything until a bit later. Assumed a reboot but that wouldnt explain the loss of all the other settings. Sound right?

Good to hear that you got it sorted out.

I had the PCM reboot today. Was talking on bluetooth phone (blackberry) and the PCM rebooted. Came back in about 15 seconds.

How do I find out when the car was built?

Look on the drivers door jamb....it should be there just like the 997.

Rip-off
 

Get this fixed while your vehicle is still under warranty. My Cayenne is no longer under warranty and when I called the dealer I was told that the Radio had to be replaced! They wouldn't even look at it to see if it needed a software update or need a disk/storage unit. I asked for a price - $4200 big ones. Porsche dealers have a monopoly here because you have to be a licensed dealer to have access to programming the unit. So it can't be fixed in the aftermarket. So, when your vehicle first starts doing this, get it fixed under warranty or sell it!

lol .. for $4200 I would of traded it in ..

PCM Re-booting in my Porsche Cayenne
 

My experience with rebooting PCM (on Cayenne TT), is that the antenna cables behind it were not seating properly, especially the GPS antenna.
Once I used zip ties and glued a plastic base to thread zip ties through it, to hold the end of antenna tight to the back of PCM, rebooting stopped.
I assume programming for the PCM scans for connection to signals, and if signal goes in/out frequently, PCM does a reboot to reset itself.
Since I did the zip tie thing on the Cayenne, I have not seen one reboot yet, thats about 2 years now. Before doing so, I would have reboot often, especially when using GPS.
I have a thread on this somewhere on here, in the Cayenne forum.

Ciaka what year of Cayenne do you have? I am experiencing this issue on my 2015

Mine is 2005. The gps cable connector is tiny and brittle. If Gps cable is loose it causes PCm to try reset itself. After reset pcm checks again. If not fixed. Reset here we go again.
removing radio should be easy to look behind.

Very interesting this thread resurfaced as this happened to me this AM in my 2011 Panamera Turbo - I have issues w/ entry & drive // the driver door lock/actuator - I recently had a bad tire swapped out and im thinking this may have something to do with memory as I manually locked the car last night and manually unlocked it this AM... will see how things progress but I have enough on my plate as it is and dont need to add a new PCM to the list :(

Porsches are very sensitive to voltage variations, so make sure your battery is good and charged up too, to eliminate that possibility.

apparently this is happening to many panamera/cayenne owners - has to do w/ sirius XM

Happening to me this morning in my Panamera while using XM. Very upsetting...