Over the past few weeks I've noticed that while my 97 900 Turbo's engine is on, the lights in and outside the car flicker, over time the car has started jerking in time with the flickering. I've determined that it's not the battery, because when the car is off, the lights are fine running on just battery power. It's becoming more and more difficult for the car to turn over, but it eventually does. I'm pretty sure it's not the alternator itself because I got a new one a year ago. I'm about to start a long trip so I need to get it fixed. Let me know