T5500 turn off-on in cycle with a new PCIe Wi-Fi card

Hello. I recently got a wifi pcie card to spice up my old but powerful T5500 (dual Xeon X5660 with 48GB DDR3 ECC). The wifi card works fine but when I try to turn off the PC, it turns on by itself and turns off again after a few seconds, in an endless cycle. It only stops when I unplug the power cord, and happens again on the next power off. No BIOS events reported.
I have the latest BIOS version available (A16) but I can't find many options that may be related. I disabled WoL, internal NIC and C states, but no change.
Changing pcie slots makes no difference. The problem is solved when I remove the card.
There are no other problems with my T5500 except for this.
The wifi card is based on the Intel AX210 controller and I have all the latest drivers (Windows 10 x64).
Will there be any incompatibility or maybe some interference problem?
Do you know any workaround?