OS Catalina on my iMac & shut down

Sometimes mu Imac shuts down, but staight away it reopens with a spinning white wheel at the bottomm of the page.

So, my alternative is to use Shift>control>option and whilst holding these down, press the on / off button on the mac.

I have reported this several times to Apple over the past few months. Buthey do absolutely nothing, even bringing out a new software update last week that did not fix this problem. They have become totally arrogant towards their customer base. All they are interestd in is sales...sales ....sales. Last Mac I ever buy. Even got rid of my Iphone and Ipad. Now using Android.

Once this mac is dead I will never buy Apple products again!!

Did you have time machine running before your upgrade, and if so, did you delete it and made sure there was a completely new time machine backup before turning your mac of?

It really helped me. I can even shut it down again while making a bakup. I think it's somekind of time machine bug.

I feel bad for complaining, because you all have newer macs, mine is a late 2013, lol. But I'm getting the same problems, it started a long time back, well with installing Catalina. I had a bad disk thing happen and I think it was the intitial disk conversion program they used to convert from HFS to APFS. I reinstalled using a fresh install media on a usb and that fixed all the Disk Utility errors. But soon after all the above continued. From a fresh startup to opening Firefox and browsing can take a good 20 minutes, so I leave the darn thing on. It won't shutdown, it won't restart. Lately it verifies programs over and over, and I can't install anything unless I boot into safe mode. Everything just doesn't work anymore. Right now i'm exporting all my photos onto an external drive and clearing out all my personal stuff and going to try and reformat completely etc. I have a small Linux partition from where I run Arch Linux and it works like OSX use to. Two bounces and Firefox is ready, never crashes, and is zippy like I got an SSD or something. Spotify Desktop opens immediately. I'm converting over to Linux, already dumped the iphone for Android, I'm going to try and use this iMac for a while with dual boot, but am going to go get a new computer that won't be a Mac for the first time in 25 years (Performa 6400(?). I'm not really sad or mad about it, I've went a bit geek too, so it's time. I want to work with photos and all the rest and Linux has better and free software to manage stuff. I've reset the SMC, NVRAM over and over again, quit Time machine, restarted Time Machine, turned off all memory hogs and on and on. Obviously, judging by the length of this thread and it's volume, Apple doesn't have any answers, and we're 4 major updates into this...it was a good run, it's time for us to part ways.