I don't know exactly what it is, but if it were me, I would guess that a fuse, or some other electrical connection has either a hairline crack or is dirty or ??, and that once it gets warm enough, thermal expansion gives sufficient contact. So, I would be checking fuses and electrical connections with a fine toothed comb.

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D