Thanks for reaching out. It seems that FF might be doing some background processes in your device or you might just be running out of RAM. I opened Firefox on my older (2009 model, 2GB RAM) PC, with half a dozen tabs running, it occupies only 12% of the memory. Possible fixes: 1. Check your FF settings for unwanted permissions etc. 2. There might be a hardware issue that needs a professional look. 3. If it's not too hard, reinstall FF on your device.