That's weird, a MT242H isn't that old so it shouldn't have starter problems already, but if it works after hitting it with a hammer, it does sound like possibly a starter problem. But first make sure the connections on the starter are clean and tight. I have seen the flat push on connector on the small wire that energizes the solenoid not fit on tight enough and cause an intermittent no crank problem. Sometimes after leaving it sit for a while it started, but then happened again later just like yours. When I pulled the wire off to check it, it pulled off with almost no effort so I squeezed it with pliers so it pushed on tighter and the problem was gone for good. Possibly tapping with a hammer is making the loose connection work while cranking. LS tractors are not known for problems with the starters (although nothing is impossible). My dealer only saw one that needed a replacement and that tractor was 10 years old. Good luck and please let us know what you find. If the starter is bad, it would fall under the 2 year bumper to bumper warranty. That's what they call it even though they don't have bumpers
