Strange FPS drop in Mass mass effect

The trouble is that if the GPU is running from the CPU or MoBo, it means system resources will be used a lot more than a laptop with a seperate GPU with its own memory. If you have installed software in the background like AV softwares and whatnot that you haven't done before or is a different software, it can also consume those limited resources even more as memory and processing power is consumed by those programmes.

Also keep your computer up to date and run a cleaning software to remove invalid registry entries and old files just cluttering your hard disk. if you have a standard HDD, consider defragging the drive every so often in order o boost performance.

some graphics drivers are capable of making games run better or worse, sometimes even when you run the most up todate Nvidia driver it could have an issue that means it can't run that game as well so reverting to a previous driver might be needed. in any event keep on top of your driver settings. In addition consider what settings you are running on your Nvidia driver as well, there could be something in that, that may slow down your performance.

for the game take off shadows, AA and adjust the various controls to adjust the texture settings. In order to keep your frame rates as stable as possible, make sure to check your v-sync.

As Holger mentioned, more details are needed really to find out specifically what the problem is.