I don't know much, but if the battery runs down that quickly it may be the issue - gains charge so starts after sitting a short time but loses it after sitting a while. Most auto parts stores will test your battery for free. How old is the battery?
Another possibility that I've run into before was the fuel pump. Mine started going out, so it would start if I had not let it sit for too long, but overnight or when I got off work the fuel pump was letting the fuel in the line flow back into the tank, and it took it quite a while for the pump to get fuel back up to the engine before it would start.
02 Ranger XLT 4x4 Off Road, 4.0L SOHC, Automatic, 8.8 4.10 LS, Super-Cab, 3" Body Lift, 33x12.5x15 BFG All Terrains on 15x8 M/T Classic IIs, 5K 55w Heads, 5K 35w fogs, custom front skid plate, various other goodies.