it is a 91 Civic Si which recently started to just die on me. It happens only when I have been driving for about 20min. when the engine is warm and after waiting a minute it starts again. There are no noises the engine just cuts off. And it does not happen when the weather is cool. Engine is not overheating according to temperature gauge.
what could be the problem

 

your distributor is shot get a new one i had the same problem

 

could be your ignition switch, happened to me.

 

could also be Main Relay