iphone 4s black screen when sim inserted

Bought an unlocked iphone 4s, reset using itunes, and restored as a new phone with all my WIFI, icloud etc. all worked fine. Turned phone off, inserted my sim and screen went black, it was still powered and after ten minutes was very hot. I tried resetting buttons etc, no good. plugged back into itunes and it all showed on the laptop but still black screen. Took sim out, reset factory settings with itunes, still nothing. two days later plugged into charger and all worked again. went through set up process, placed SIM in and its went black again. Cant get it to work and its just hot now. I assume that it should work again in a few days when it drains and I charge it again. Could this be a battery issue? why is the sim creating the problem? 😕 PS it has updated to the current IOS 8.4, but behaved the same on its older version on first start up.