Do you happen to know if it's the stock shifter or if it's an aftermarket shifter?
First thing, just check if the knob is loose on the handle. If it is, then you may need to pry the plastic bezel off (that surrounds the bottom of the shift boot) and see if the base of the shifter is securely attached to the transmission. It's just 4 bolts that hold it on...that is, if it's the stock shifter.
If it's an aftermarket shifter, then the handle will probably have a couple bolts that hold it to the shifter "base." The base will still be attached with 4 bolts, but the handle would be a separate piece, depending on which shifter it is.