My 2013 MacBook Pro hit the dust. My battery ran dead the other day and ever since then when I try to power it back up it tells me I need to restart and when I restart it doesn’t do anything but tell me that I need to restart again

My 2013 MacBook Pro bit the dust. My battery ran dead the other day and ever since then when I try to power it back up it tells me I need to restart and when I restart it doesn’t do anything but tell me that I need to restart again. I tried to repair through utilities and that did nothing so then i went in and erased the Mac OS Sierra to start over and now that I’ve done that it’s it won’t let me reinstall because it says “untrusted cert title”.