Why is my andoird phone automatically turns off when I enable the sim card slot?

Everytime I enable the sim card slot, my android phone automatically turns off. It's annoying because it happens everytime, whether I'm using my phone or not. My 30% battery went down to 0% when I restart my phone after it turns itself off. How can I fix this?

Welcome to Android Central! Which phone? What do you mean by "enabling the SIM card slot"? Do you mean physically inserting the SIM?