windows 10 – NVMe performance lag and strange activity LED blinking

Installed NVMe in the M2 slot on Asus Z170 Deluxe.
It rocks PCIe3 (x4) so it reaches correct speeds (up to 3GB/s).
However, I’ve noticed that sometimes the system (W10) waits for the disk to sort of a “initialize” and the HDD activity LED is flashing rhythmically on and off all the time.
When I access my other SSD’s, the there is no lag and LED is flashing normally (as disk writes or reads).
I wonder what is the cause of the lag and strange blinking rhythm?