What's wrong with my DSLR? Extreme shutter lag at all times even with manual focus?

For the last few months every time I press the shutter button it takes 5-10 seconds for the camera to take the photo even on manual mode and manual focus. I have a Nikon D3100, 6 years old, there was a period of 6th months where I didn't use it and it just sat in my room… What that be the problem?

Your timer might be on.

I think regwah is correct. I did this to my D7100 and panicked for 5 minutes lol.