Slap the top of the dash above the instrument cluster. If that starts it up, check the tension on the three-pin L-shaped plug at the back of the speedometer -- its locking anti-tamper clip is probably long gone.

If the slap doesn't do it, the ignition switch is the next most likely fix. First, try gently wiggling the key while the car is running.

A third possibility is someone worked on the cluster (what 20 years ago?) and left a loose screw where its flex fuse is attached. This is the only fuse protecting the circuit you're losing, and not one meant for owner replacement.
--
Art Benstein near Baltimore

If speed counted, rabbits would rule the world.