Problem following interrupted sleep command.

I manually put my PC to sleep but as it was going down, I nudged the mouse. The screens went black as expected but I then found the PC would not wake up again. I tried a restart from the case button but the HDD light was dead. The power light was on but not flashing as it does when asleep. I forced a shutdown with the case button, left it for 2 minutes and then tried to start again but no response. I tried this a few times but then gave up. I left the PC with the power light on while I turned to my laptop to search the net for any advice but Googling just showed the expected BSOD or Safe Mode issues, or no power. I returned to the study to find the manufacturers logo on the screen, but no further response to continue bootup. All that was available was F1 BIOS option which I entered. Nothing obvious was showing so I saved and exited with no changes. The PC then started a normal boot into Windows and all was fine again.
Sorry about the protracted story but can anyone tell me what happened? The issue is fixed but I would like to know out of curiosity.

There are many issues that could have happened. You may want to run Diagnostics on the SSD/HDD's.
When an issue like this happens, turn off the PSU at it's power switch on the back of the computer. Wait a minute or so, switch it on and then power the computer on from the case on button. See if that helps.

It seems to be a very uncommon scenario that tends to happen in a sleep power state. There are several sleep state levels of which devices can work in none, some or all levels. The device will neither wake up nor shutdown. Best solution is to remove the power source and hold the power button down to remove residual charge. Any state information would remain in memory and/or disk, so it may be a good idea to validate both and ensure no defects

Thanks for the replies. The PC is running fine and booting normally again but I will run some checks to ensure all is ok.