The seat moving around at random can be turned off via the instrument panel if you poke at it long enough. I have just learned to deal with it. My 300C is in disgrace at the moment. The last running issue (that the engine computer isn't heating the O2 sensors) resulted in some pretty poor running so I ended up putting a timer based relay on them. You'll be reading this thinking "just buy a new PCM" and I will, but tracking one down for a 2006 is proving a little harder than I thought. In theory anything with a 5.7 from 2006-2010 should work but apparently there are a few issues here and there. I do have a 2010 PCM for a 5.7 but despite programming it with the VIN the car won't start, so here is plan B. I didn't want to do anything permanent while I get a new PCM, so I snipped the "power" leads on the 4 wire O2 sensor pigtails and made up a small harness to supply 12 volts. This isn't what the PCM does (it pulse width modulates a signal to them) but 12V will run the heaters. I tried this on the bench and they stabilise at around 30 seconds (using an infra-red temp monitor). I don't want to run them all the time, just for that period of time when the exhaust isn't not enough which for me is around 5 or so minutes of normal driving. The redneck version of an O2 sensor heatup is just to power the heaters long enough so that the exhaust temp takes over. Then switch the heaters off because the elements will burn out if they are powered on all the time. I bought a "Digitech" interval timing monitor from Jaycar. This thing is pretty neat: it has an "on" interval and an "off" interval that ranges from seconds to hours. In my case, I don't want it cycling between on and off so I removed the little jumper that controls that. The other jumpers control the time, so it's set to 10 minutes on and then off (until the ignition is cycled again). The timer module has a handy "reset" circuit, so I installed a small switch discretely in the cab to be able to reset the O2 heaters back to on if I end up idling somewhere for an extended period (like at a roadworks or something). The wiring isn't exactly tidy but it's good enough. The timer module isn't robust enough to mount under the bonnet so it's inside the car under the dashboard. The relay inside it also isn't quite big enough to handle the current draw of the O2 heaters, so I have an under-bonnet relay to do that. Most of the work was in running the wiring to the O2 sensors (fore and aft of both of the catalytic converters). Proof is in the pudding. Before, the big V8 would idle perfectly for 60 seconds (open loop mode when it's warming up, ignoring the O2 sensors), then start loping/stalling for a few minutes, then run fine when the exhaust was hot. Now there is no transition - idles perfectly, drops to the correct idle speed after 60 seconds and pulls away without stumbling. By the time the 10 minutes is up the exhaust is hot and the O2 sensors read fine regardless. Success! Except...what's this red oil light doing coming on? Car seems fine, oil pressure should be fine. It's not clattering, the multi-cylinder displacement is working. I am 99% sure the oil pressure sensor is dying but guess how many are available near me. Zero. Back to the shed while I wait for a replacement sensor. Have a few other jobs to complete today but will plug my external oil pressure gauge as a sanity check.