Check for the simplest and most common causes first. Start with your spark plugs. In any case, new spark plugs are always better so you should replace them. Also look for damaged plug wiring, carefully checking the entire circumference of each wire from the ignition source to the plug boot. Pay special attention to any area of wiring that comes into contact with hot engine components. If in doubt, you can use a spray bottle mixed with water and salt to squirt onto the wiring. If there is breakage in the sheathing then it will spark when coated with the saltwater.

If after you replace the plugs and/or wires and still have the problem then consider a new fuel filter.