My 2008 997 is acting very strangely. The best way to describe it is that it feels like you are disconnecting the battery for a second.

This is what happens:
- I turn off the car after driving it
- the window that slightly lowers to open the door stays down
- I need to then turn the car back on (don't push the plug, just turn on electrical) in order to raise the window
- It will show psm light

This doesn't always happen but does about half the time that I turn the car off. It seems to be more likely to happen if I turn off the ignition but leave the key in the ignition for a little longer than normal.

Any ideas what this can be?