I could be way off but if you have directional tires ( don't know in your size), they can get caught in grooves on the freeway that can cause your car to sort of sway all of a sudden. I know in Cali a lot of the freeways have grooves (for lack of a better word) and they can sort of grab at your tires. Especially when new.

 

I have the stock 17s non-runflat, non-directional, all the same size. I'm guessing at this point that I have suspension issues.

 

Agree - with certain tires the E60 is very susceptible to tramlining. Essentially, the tires do as you describe, they get caught and follow the grooves etched into the road surface on many freeways. It is a particular problem here in NorCal. What to OP describes sounds to me to be tramlining, not an alignment issue. For me, the only cure was to switch to better tires than the abysmal stock RFT's.

 

LOL. Today I put some some wheels on the car to try out. The offsets are different than the stock wheels. The aftermarket wheels matched up to OEM specs (overall diameter/offsets) and they rode GREAT. So these new wheels are a bit wider and the stick out a bit more. I noticed the car is EXTREMELY touchy on the steering. The steering wheel seems slightly cocked to the right as well. I didn't change any suspension parts in the front. I have a cracked left controller arm bushing as user HealthServices posted which I was going to press out this weekend. Other than that I think perhaps the offset is causing this. Or perhaps brand new tires. Anyone had this issue?

Regarding your issue, is this when you're only going high speeds? For me i feel the steering touchy which makes me back off the pedal when hitting 100-120mph because its not driving the same as it was prior to swapping out. I feel like the same thing ... high winds. but that's only when I play with the steering wheel. Havne't really diagnosed it too much. The funny thing is that you're all stock. Maybe its a bushing. Even with my bushings cracked previously on the E60 I never felt that. Did feel this on my E46. Could be that the new wheel offsets up front put more stress on the bushings and the cracked bushing is not holding up as it was on the previous offset.