Craftsman with B&S Flywheel not turning smoothly/Engine Shakes

I mower would not start and I found that the small starter gear was engaging the flywheel, but it couldnt turn it. The flywheel seemed stuck, so I manually turned it. It was difficult at first, but I was able to turn it...it turns freely 3/4 of the way around, then it gets tougher to turn, but it will eventually turn with extra effort. Once I did that, the motor started, but it shakes and vibrates really hard, to the point I shut it off as I didnt know what the problem was. I am hoping my engine isnt shot. The mower is about 7 yrs old. Craftsman 21HP Twin B&S

Stupid question, have you checked the oil level? Sounds like the engine started to run tight.