HELP! My '03 Beetle just died today

I have a 2003 VW Beetle GLS...I drove it this morning and it was fine. Low on gas, so I fueled up a bit, but fine. I turned it on and off a few times with no issues. Then, I got home and tried to lock it with the keyless entry remote and it did nothing. I thought nothing of it and went inside. When I came out maybe 25 minutes later, it was totally dea.d The odometer wasn't even showing up. I replaced the battery a few weeks ago. I opened the hood to see if it was something there, not that I have any idea what I'm looking for haha, and when I tried to start it again, it had power for a couple seconds and nothing since. Is it a fuse? Is it the battery maybe? I'm so lost as to where to even start. Any help is greatly appreciated!

Sounds like the alternator is not charging resulting in you battery gradually losing charge. You could check this by either charging your battery or substituting it with another known good unit then start the engine and measure the battery coltage at idle - it should be above 14Volts. If not then the alternator is buggered...or the belt that drives it is off.
In theory if it was the alternator failing then you should have had a warning light.
Good Luck.