It could be several things. When was the last time your brakes were repaired and if so, new brake rotors? If brakes are worn and rotors worn, when coming to a stop they may wobble. There are numerous things on the front end also that can be lose, tie rods, ball joints etc. For free you can go to a reputable front end shop and have it checked out. You have a large number of miles on your vehicle so it has been good to you. It is probably past time that the front end is worn.

Misfire, you may be in need of a major tune up this which will include sparkplugs sparkplug wires and maybe even a ignition coil