Today's cars have multiple systems in them that are managed by processing modules (onboard computers).
The Gen1 300's have 9 such onboard computers. Early models, especially year 2005 had some software glitches - that were corrected with updates performed by dealership electronic technicians, using the StarScan tool.
If you are starting to experience various electronic gremlins, the first thing I would start with is to ensure that your battery is still working well. Typical battery life is 5 years. It must charge up fully and hold the voltage output. Battery connections must also be cleaned and tightened.
If the battery tests out well and current is flowing well through your system, then I would find a good service department to first print out a history on your car (every dealership has your information in their computers). You can see if all of the software updates have been done. If you need a few of them to be done, you should be able to negotiage a flat fee to have them all done at once.
Here at 3CF, we have a great resource for this stuff:
Hope this helps!