4WD Robot and Servo interference/shaking

Hi all, I’ve a problem with an hypotetical interference between 4 DC motor and 2 servos (see the attachment for the schema).
If I use the servos separately there is no problem, but when I use it together to the DC motor, the servos going crazy (shaking, move rapidly to the limit position).
The servo’s supply has already separated from the dc motor supply.

Help me please.