Windows 10 Automatic Repair Loop on 4K iMac

Hi,

I need help urgently, as I have very important documents on my Boot Camp Partition.

I have been using Windows 10 on my 4K iMac for about 4 months now. Everything seemed to be OK. I have previously had to delete the partition about 3-4 times, as it goes into an Automatic Repair loop. I have just arrived home from a holiday, and I found that my iMac wasn't booting into Windows 10. I have tried downloading the installer to a USB drive, and using Command Prompt. That didn't work. I can't reset the PC, I can't boot into Safe Mode. Is there any chance that I could get back into my boot camp partition, otherwise it will cost me lots of money and time in deleted files.

Thanks for any help given

Leo