Please help! Car won't crank when hot. Works great when cold?

Thanks for the response. However, let me revise my question. Engine starter will not engage when motor is hot. If restarted immediately, the starter will engage and run without issue. However, if allowed to sit 15-20 minutes, it will not even crank. It is as though power is not reaching the starter. Seems to be obviously heat related. I have replaced starter/solonoid and established a second ground so far with no different results. Any further suggestions?

Thanks again for the response. And yes, I agree. I believe it is either ignition switch or neutral safety switch. Looked up how to replace neutral switch and looks to be a pain since it is located on top of the transmission. Decided to bypass with hotwire straight from battery to starter then starter to toggle switch under the dash. Bypassed all the relays and switches. Now starts like a charm. What is strange though is that when I start with bypass toggle then turn back off. It will start again immediately the next time with the key no problem. Not sure, but I appreciate your help.