Q: The car starts fine the first time, but then has difficult startup

The O2 Sensors or the Mass Airflow Sensor may be bad. The list can go on. The engine computer will need to be tested and all codes diagnosed. Since you drove the vehicle for a year with it running this way, it could cause other problems like carbon build up in the engine and possible catalyst damage. If the engine is running rich, then there is a reason for this and only a thorough diagnosis of the engine control systems by a qualified mechanic, like one from YourMechanic can isolate the cause. I recommend you contact a technician, to inspect why your car is hard to start before making the necessary repairs.