Starter? 1994 Chevy S10 Blazer
 

Have had to replace multiple starters in the past four or so years. About four times now, replaced the battery, battery cables going to the starter. Not sure what else it could be? Flywheel maybe? How do you check to see if the flywheel is bad?

check the teeth to see if they are ate up, if you have an oil leak that drips onto the starter, it tends to kill them quick.

your starter may be overheating and the frying the solenoid. Try wrapping it with some heat wrap (silver shiny fabric) and your problem may end.