I’ve faced this a couple of times, and this is what happens -
I face issues with peripherals - HDDs, keyboards, mice, sound cards, what have you. I reset the SMC and sometimes they work fine. I try to do a PRAM reset and the Mac mini goes into an endless reboot loop. If i forcefully turn it off by holding the power button and then boot while holding the alt/option key, I get a choice of hard disks to boot from, and then I boot into normalcy (so to speak). But I have a nagging problem with a bluetooth keyboard (another post of mine) that I think the PRAM might solve, but I’m now stuck between the faulty keyboard and being able to get work done. HELP!