I had a similar issue with my new Mac mini (I've had it about a week). Earlier this week, the Mac mini would not wake from sleep (or at least would not wake the monitor up). I have a wireless Apple Magic Keyboard, wireless Magic Trackpad, and wireless Magic Mouse connected via Bluetooth. Nothing would cause the Mac to wake up. I contacted Apple Support and they had me do a SMC reset by powering off the Mac, unplug the Mac and wait 10-15 seconds, plug it back in and restart. It's work fine since then.
Other than that I've been very happy with the Mac mini. I got the Mac mini because my 2015 MacBook Pro started to have onboard memory problems which I need get resolved. In the past I've also had a 27" iMac (which was stolen when our house was broken into). Never thought I would like the Mac mini, but I'm quite please with it.