Odd noise when first starting it?

The other day my car started to develop an odd noise when first starting it. It's almost like a pretty loud rattle. It would go away after a minute but a couple days later it started to stay longer and longer every time I drove. Yesterday the dash lit up saying something along the line of "Service Charging System". I have a short video to show the noise (camera cut off without me knowing so it's only 3 seconds so I apologize.) Just wondering if anyone can maybe pin point the noise or have dealt with a similar noise before? Thanks!