Have a vibration 45mph to55mph and the goes away about 70mph

What is your question?

when I first start out acts normally then as time goes on it gets worse. I have had days where I was ok up until 60 then ays where i can't get over 45. I feel it in the front end and the vibration win loosen the collum lock.

What makes this problem better or worse?

when i first star moving i'm ok up to 60.

How long has your 1994 BMW 325is had this problem?

I bought the car 4 months ago and have replaced the tires.