I thought as much.
The wires are corroded, making intermittent contact. I think the wiring may need more attention. The bomb feels lazy, and the warning does indeed come on after a number of seconds after starting. Occasionally, the warning extinguishes, but i expect this to not last long.

85 WR quattro
90 V8 Silver, 91 V8 Black, 93 V8 Lago
93 100e quattro V6. Titan, i think