Bad motor mounts can cause the engine to "shudder" when you turn it off. As for hard starting hot or cold, that can be a number of things. You can start by checking the valve clearance(cold engine);Check the dampening screw on the rear of the injection pump.Make sure it is not screwed all the way in;Check fuel pump to make sure it is delivering enough fuel at cranking speed. Last but by no means the last reason your engine is hard to start, is do a compression test on each cylinder.For non turbo engines the normal pressure is 22-24 atmospheres(hot engine)Minimum pres.about 15atmos.
Max. difference between any two cylinders is 15atmo.For turbo engines the normal comp.pressure is 24-30atmo. I believe one atmos.equals about 14.7psi.
Good luck with your starting problem
Bill Lewallen Lexington,Ky.