1991 Suzuki Sierra Violent vibration while driving

Hi, I have a 1991 Suzuki Sierra with 200000km on it. Over the last few months it has developed a violent wobble while accelerating or deccelerating through 40-60km. It is worse when it is cold. It started as a small shudder but now the steering wheel is violently thrown from side to side and it feels like the car is jumping off the road. The car doesnt noticeably move from side to side though, even though the steering wheel does and when stopped there is a lot of play in the steering wheel (could be a seperate problem). What do you think is the cause and how much roughly to fix it?