I am having a similar problem with my Dads craftsman riding mower,it started with a vibration, I cut it off and the bolts on the left deck for the blade rotation were gone, I replaced, tightened and put belt back on, checked out everything.Cranking back up when I released clutch and or went to engage blades mower cuts off.are there safety switches for this or do I have another issue?help would be great, Dad passed away and I maintain property,am on a short budget

Hi,
This is generally termed operator presence; the machine must "know" that the seat is occupied by an operator. Generally a seat switch problem.
Peace,
Clarke