From the intermittent perspective, it sounds like a pushbutton controller problem. The internal circuit boards are arranged in an "H" pattern with solder joints along the edges. Over time these solder joints develop hairline cracks and give you very intermittent problems.

If you do an "advanced" search for "pushbutton controller" and "resoldering" you should find serveral threads concerning this and likely some photos as well.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )