Electrical Problem ? windows,seat power,mirrors on 1999 Mercedes-Benz C280

Windows all or some stop working,power mirrors stop, some time only one,power seats stop. OK when I disconnect battery everything will be perfect for a few days or week. then problem starts again. I checked all grounds. I think the problem is the part under passenger side floor carpet thair is a electronic part under plate looks like a control Modual. I dont know whar it is called.?

Asked by for the 1999 Mercedes-Benz C280