Engine has trouble starting

I have a 2003 Tacoma 3.4L V6 all stock, and I have noticed that the engine starts great when cold (sitting overnight) but has a hard time starting when its only been sitting for 2 hours. The engine turns over and tries to start but then stalls out. I have to pump the accelerator pedal a few times and then try again which usually works. Could it be a bad battery or does it needs new spark plugs? When I bought the truck a few years ago, the battery case was loose and I was able to move the battery freely. The battery was still fine even though it bounced around before I secured it better to the battery case.