This is something that I hear about with some turntables. I can't say that is your issue for sure; however, when a turntable motor starts up, it sometimes takes a second or two for the motor speed to stabilize. It is possible that the motor gets going, the platter accelerates, the inertia of the platter, as it accelerates to speed, actually causes it to rotate a tiny bit faster than the proper speed. The motor then stabilizes, the belt grabs the platter and slows it down to proper rotation speed, which is what the shudder may be. It's all over in a few seconds. So if your table is a fine a few seconds after this initial start up, I wouldn't worry.