Weird Noise

I drive a 1996 Toyota 4runner SR5 with 121,000 miles, 4 wheel drive.
Sometimes I go to start my truck, and it doesn't crank. The lights come on inside the vehicle (like the brake, check engine, seatbelt lights. Etc.).
Then other times it will start, but makes a really loud noise. It's coming from the front of the truck, but I'm not exactly sure where it is.
Another day I started it, and it was making that loud noise and the brake light came on. So I checked my parking brake and brake fluid, and both were fine. I let the truck keep running, then all of the sudden the check engine light flashed once, the car cranked and then the loud noise stopped and the brake light disappeared and everything was fine.
Do you have any idea what could be going on?
And just to let you know, I've recently replaced the battery and alternator.
Thanks for your help!