I have a Deere la110 that started but then stopped after five or so minutes. I tried to restart and it cranks but light blue smoke came from the exhaust for the first three cranks. Will still crank but no smoke and will not turn over. I do have it serviced annually. Most recently I did run over a rock but it continued to run after that. Any thoughts?

Did the blades hit the rock or just the wheels and/or chassis? How long before it will restart? Try removing the gas cap and see if it runs longer.

Okay you said it will crank , but not turn over .Please explain this.
Could be a sheared fly wheel key , and Bob is right
Could be a simple as a gas cap.
Luck

To me, cranking and turning over mean the same thing. Firing is something else, you see puffs, smoke and the engine coughs if its firing even a little.