I am confused, is it engaged and turning the engine or just setting there, not turning the engine and running?
#1. Solenoid contactor plate self welded to contacts.
#2. Possible key start switch fault, mechanical damage is most likely here.
#3. Possible dirty centrifugal clutch = locked engaged with fly wheel.
#4. Possible broken solenoid contactor plate, return spring.

To bad you are not local; I would like to do forensic diagnosis on it.

I hope that you took no offence from leathermang or myself, none was meant.
FYI, if you do a search with no results, please mention it in your post.
Many senior and founding members do get tired of answering repeat questions, when a simple search could find the answer.

Some of us are as subtle as a sledge hammer, especially on a rough day.
__________________
ASE Master Mechanic
Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer
1985 300SD
1983 300D
https://www.boldegoist.com/