A few things come to mind. Some of them have been mentioned above, but I will add them in my thoughts as well.
1. Your fuel tank is low. I notice in my car that when the tank is below 1/4, it requires more starter turns for the vehicle to start. One thing that may help is to turn the key to the run position and wait for the check engine light to go off before you start it. This allows the fuel pump to build some pressure in the system.
2. Your fuel filter could be getting plugged. When is the last time it was changed?
3. Your fuel pump may be failing. Doubtfull, but if you have had a plugged fuel filter for awhile you could be putting excess wear on it. Constantly running the tank at a low level can also reduce the life of an in tank fuel pump. The pump uses fuel in the tank as a lubricant.
4. Your battery may be failing. You can take your car to any auto parts chain store (AutoZone, Advance, etc.) and they can do a load test on the battery. They should do it for free. If they don't, go somewhere else.
5. Your starter may be failing. Again, you can take your car to any auto parts chain store and they can do a starter load test to see how much current the starter is drawing. Starting current should be no more than 270 amps.
Good luck!