Dell Precision Workstation T3610 booting delay

We have 3 Dell Precision Workstation T3610 in our office. All the 3 PC's taking 5 minuted to boot if there is a network cable is connected, we have formatted with new OS, but no luck, upgrade all driver and bios and the HDD rate is 5.9.

Is there any issue of the Mother of board/NW card of this model? All other PC in our  office is working fine