when cruising at moderate speed (40-50miles/hour) steering wheel wobbles left righ when I take hands of it

it's not strong, if I hold the steering wheel the force doesn't transfer to the hands and I can say it stops. but as above - if hands off, it shakes left-right quite noticeably.
no vibration under braking
alignment is done on all four, 0 toe all around and -1.8Fr/-1.5rear camber

what can it be ?

 

Possible out of balance or bent wheel