I just bought a used mudbuddy SD and noticed when I was running it I felt a vibration in the handle as I was running is this normal or is this the first sign the bearings are going out?

Could be prop out of balance. Is this your first mud motor? There is always some vibration, how bad are we talking?

Kind of stupid but it could be something wrapped around the prop cut grass , fishing string , ect ?

You would be able to see it if it was that much

new prop but this is my first mud motor the guy i bought it from put in the new parts and so not sure how well he did it just trying to see what is normal i would say it vibrates like a weed eater with a heavy brush blade if that makes

also i have tried everything to get the seal nut off and he must have used loctite or somthing because it wil not move so i will have to heat it to get it off so i dont want to do that if im worried for nothing
Yes i do know the seal nut is lefthanded thread

You mean the prop nut, or the seal cap?