Sudden shutdowns on low battery

My computer was working just fine a few weeks ago, but lately it hasn't been reacting properly to low battery levels. Instead of giving me two warnings and then going through the shutdown process, it now gives me no warnings and then there's a physical click as my screen goes black instantly. When I plug it in and turn it back on, it asks if I want Safe Mode or Normal Startup, and it does not restore any of my windows as it would if it went through the proper low-battery shutdown process. Can someone explain why this is happening, whether it is harmful, and how I can make it work right again?

Thanks!