Car trouble

While driving home from work last night, I recieved quite a shock. When I went to turn left onto my road, the car fought me so hard that I nearly drove into the neighbor's fence. My husband, henceforth to be known as CG (computer geek) drove it and it did the same thing to him. We had his brother - the handy mechanic - look at it, and he's really not sure what is going on either. It doesn't do it when the car is in park or in reverse, and it doesn't do it when trying to turn right. So we've got an appointment to have it looked at tomorrow morning. I'm trying very hard to not stress. I mean, this is a new car (to us anyway). There shouldn't be anything wrong with it. We believe it is still covered under warrenty, so hopefully the repairs shouldn't cost us anything. Even if we do, we have our tax return coming so it's not like we would be stuck with a bill we can't pay. I just hope it is a simple fix.