Sporadic power seat
 

I have a 99 Boxster. Recently, the driver's seat works sporadically. It's fine when parked, no key in the ignition. It's seems to work after I start it up. But it stops working after I start driving and even after I stop, put it in park, take the key out of the ignition. After it sits a while, it starts working again. The fuse if fine. It appears that the brown ground wire is intact and shows no sign of moisture. I can't find any threads that cover something like this. So, I don't know what else to check.