when a lot of electical or electronic items start not working properly low volage sometime can be to blame. you stated that the car hadn't been driven in 2 weeks prior. You may have "a slow to react" voltage regulator in your alternator not charging the battery up fast enough. By driving it this week you have charged the battery back up. the "power on master reset" reboot ( I am an old electronics/main frame guy)" just cleared all the rubish, stuck registers, etc. and reset everthing.

just a thought and good luck!

Steve
1992 W140 300SD