Front load washer, jerks when it starts to spin, then smooths out

on many machines that is normal, the shaking continues until the load is distributed relative evenly around the spinning drum. It is also possible it is the main bearing but I am not sure. The noise I am talking about would have been there since new. These links may help. Washer has noise during spin cycle Whirlpool Maytag Sears GHW9100LW1 Washer is Making Loud Noise
How To Fix Washing Machine Making Noise During The Spin Cycle
http://www.partselect.com/Repair/Washer/Noisy/

The wash drum should spin smoothly by hand without much noise. It is supported with two sets of ball bearings. If the water seal fails, water starts to leak into the inner bearing and they start to rust causing a loud noise especially during the spin cycle. The only way to fix it is to replace the bearings and seal. It a big and expensive job to replace the bearings since you literally need to take your washer apart to get to the bearings. Sorry.

you are putting an uneven load into it ,ie a couple of towels and a pair of socks if you get what i mean,try waiting until you have a good load before starting a cycle you will see the problem is not there anymore.adrian,,,,

Mine did that and had to have the washer re-balanced.

If it is brand new are the transit bolts removed? try spin with nothing in it and see if it turns smoothly, if not there is something broken inside, id spins smoothly it will be a fault in the dampers.

may be a belt problem since you have this sound
thank you

if you have the spin sense option, try enbaling that on the washer

possible rear bearing gone

turn the tub on the inside if it feels ruff as it turns and makes a noise then most likely you have a bad rear bearing, if it is smooth in turning and no noise then turn to drain or spin possibly something stuck in drain pump. the drain pump will start up first if you hear the noise then the drain pump is accessed from the front lower cover, if its the rear bearing probably not worth fixing about 400.00 in parts and alot of work.

The easiest way to solve this without taking the machine apart is to tilt the machine back and look under it.
Above the transmission and clutch you will see the brake assembly. It is a little aggrevating to get to with the cabinet on, but you can spray it with some silicone lube and it will help this problem. You may have to spray it then put into spin, stop it and spray again. After it spins and stops a few times it will usually smooth out.