Stop & Go backup service

I have an iMac running on Mojave 10.14.6 using a new WD My Book 4 TB external drive to hold Time Machine backups. This drive works…then fails. Whenever I restart my computer this drive works …then fails. Each time I restart, WD discovery opens as if a new day is here, clear, bright and promising good things. Previous backups remain on the drive (which is very good).

I performed the Complete Drive Test in WD Drive Utilities. Two weeks ago it passed. This morning it failed. I will restart my computer and run it again.

Is this situation common, or peculiar? And is there a solution?