Hello, this problem is related to two things, BIOS or a bad mounting, first try to update your BIOS to the latest version, which you can find it [https://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/thinkpad-t-series-laptops/thinkpad-t440s/downloads|here].
Second if that doesn’t work, remove your RAM, use an eraser to clean it’s pins, blow some air on the stick plug then put it back.