Oh boy, it could be a slew of things. Right off the top of my head, bad fuel pump, fuel pump relay, faulty crank/cam sensor, faulty TPS, bad ECM, dirty injectors, cracked coil, bad fuel, dirty throttle bore, over heated injectors, poor/loose connections, in need of a tune up, and so on.
You'll need to do some diagnosing, and better laying out of the problem, as in hot or cold, certain speeds, weather conditions, what you've done, etc. to help us help you.
But for starters, look at the basics. Make sure all your battery connections are clean and tight, both ends. Then on to the tune up stuff, to check conditions. Make sure the basics are right before looking elsewhere.