It may or may not be the gas. If the engine is running well enough to drive your car just burn the fuel in your gas tank driving as you normally would. Refill the fuel tank with a name brand quality gas of the correct octane rating for your car. If the problem goes away with the new fuel then chances are that was the problem. If the starting problem is still present after refilling the tank then you may have an issue that needs to be looked at by a qualified service technician.