Put a kill switch on the car. Crank the engine with it off and then turn the switch on while cranking. That will solve the problem if its a timing advance issue.
To see if it is the timing take off the coil wire when its warmed up and see if it turns easy. If not , You have a starter or tight engine issue. Incorrect ring gap good be your problem if the engine is tight,
Had a small block chevy here that was tight and it broke the ring lands on every piston between the top rings from tight ring gap. For your sake I hope its the starter or timing.