Steering feels out of Control

Hi, I have a 1991 Bronco XLT, 4x4. Problem is the steering seems to overcorrect when barely turned. When let go of it is almost perfectly allligned, goes pretty straight down the road. I have 4 very good tires and balanced. It wasn't too bad before today, I just noticed when driving a normal straight road when just normal steering it would start to fishtale a little when barely moving the wheel. Then today I was turning a corner. And about a half a block later it suddenly started fishtaling like crazy and caused me to weave back and forth as if I was a drunk driver or something. And no I was sober. Very scared. Almost lost control. The road was dry also and I was not going fast maybe 25-30. Just starting to pick up speed after turning. It lasted about 5-7 seconds then all of a sudden steered normally again. It felt like I was on ice or something, but dry like I said. About a month ago we had a lot of snow. And I used the 4wd alot, and it made a couple of clunking sounds from the front driver side and the rear a couple of times while I was turning the wheel to back up. Don't know if it's related, but it didn't make the noise when the 4wd was off. It's a push button on the dash 4wd. Shortly after is when the whole steering thing started. Any clues or ideas would be helpful.