when switch is turned on, starter kicks in

What switch is that?

Sounds like the ever so popular ignition switch problem, you will have to replace and adjust properly the ignition switch down on the steering column.

when i put key in ignition and turn it to on, the starter winds over

Still sounds like an ignition switch.

tennisshoes is correct

my switch is in the dash, not on steering column

Same thing just an older design.

I just remembered a long time ago I had one in my shop that did the same thing even after I had replaced the ignition switch, found out the nuetral safty switch had come apart and the backup power contact lug came loose and had arched itself to the crank wire on the switch, so everytime the key was turned on it would crank, but I never saw another one do this, it's always been an ignition switch.