Q: Struggles to stay running when I start it and only last about 15 seconds

There are many possible malfunctions that can cause a engine to stall. As long as the engine is in good mechanical condition, it comes down to the engine getting the correct air/fuel supply, a sufficient ignition to fire the mixture, and an unobstructed exhaust to allow the gasses to exit the system. With that said, there could be a clogged fuel filter, failing fuel pump, clogged catalytic converters, an electrical problem, failed sensor, a vacuum leak, a failing ignition coil, bad plugs, or any number of other possible problems, that will cause the engine to stall. The first step would be to identify if the problem is with the fuel supply, the ignition, or the exhaust. Then, it will be a matter of identifying what component(s) in that system are causing the engine to stall. If this is a task that you feel you need a hand in identifying, and repairing, contact a certified mechanic, like those available at YourMechanic.com.