I have this problem every year, starting around November/December. You can change your update time window in settings control if a time other than the 2-4am works better for you (to troubleshoot at a different time of day).
I found another post about a Cox DVR produced by CISCO. The person had found the problem resolution by searching the CISCO websites. I have DVR Contour Record 6. I used to unplug all (including coax) for DVR and router and wait 30+ minutes before plugging back in (sometimes doing this multiple times), but after reading the post from the guy about the CISCO box (mine is not CISCO, I think it is this "Arris XG1v3 High-Definition DVR Receiver), he indicated it was an HDMI error so I've been able to minimize the troubleshooting now by following that info. Cox support and a few techs may understand the problem, but they can only "fix" it by giving you a new box because the next day's update will drop you back into boot. I very happy on the days I get up and still see the time on the display instead of boot.
I unplug the power and HDMI cable from the DVR, let it sit for a while, and then plug only the power back into the DVR. Watch the display, if it can bypass boot to config and then the time, it should finish the welcome screen load within 5 minutes or so. After that, I plug the HDMI cable back into the DVR box and live TV usually comes up within about 30 seconds (or longer if the welcome screen or three dots are still loading, as long as the time is on the DVR display and not boot). Sometimes I've seen the DVR display change when I turn off or on the DVR/TV power, but I think that may be coincidental timing.
You may have to unplug/replug the power a couple of times to make this work so don't immediately give up when boot displays, wait a few minutes to see if the DVR will recycle power and the power recycle (the DVR makes a startup humming noise) will sometimes kick it out of boot. If I go through one of those cycles and it's still on boot, then I unplug/wait/replug the power to the DVR again. All of this happens without the HDMI cable plugged into the DVR box. Thats only occurs at the very end to get the live picture back on the TV when the DVR is fully recovered. If most people have their software uploads on the default 2-4am time, then the system is busy connecting every device at the same time so you may have less problem recurrence with a different update time.
I get up around 6am with my pets, but I will sometimes unplug everything and wait until after 7am before doing recovery attempts, just assuming fewer boxes are trying to connect then. Then I leave my main TV and DVR on all day (even if on mute) just to be safe. Many times, but not all times, the recordings still record, but you can't get to them until you fix the problem. And, when you unplug/replug power, your recording will most likely be interrupted by the times that you're not plugged in. I do not schedule anything between 2am-8am to record or I know I either have to get up early or the recording is subject to being missed/interrupted. In the early years, my second TV would still work while the DVR was still stuck in boot, but now both TVs error out on the signal.
The original poster with the CISCO box did say if you replace the HDMI cable with another connector option between the DVR and your TV, that it would prevent the problem from recurring, but I haven't found a connector to work the DVR to my newer TV. Since every Contour box you get is remanufactured, they all eventually wind up with the same problem - whether it's parts or the software uploads causing the problem, I'm not sure.
I researched the cloud DVR storage, but there's still so many complaints of problems (plus I'll lose what's on my DVR now) I haven't switched. I did go into a store to get more info (Wifi requirements, box requirements, storage limitations - though I just learned on here that you can only keep recordings for one year regardless of space usage) and a cost estimate, and it was equivalent to my current monthly cost with the DVR Record 6 plus one extra TV. There is not really good information - support or sales - on their website regarding the Cloud DVR.
It's virtually impossible to "empty" your DVR and switch boxes without loss of some programs. In the local Cox store, they're using the streaming device, but have no cloud DVR solutions on display to show you how it works - that was disappointing. I wish there was a more reliable way to get information on the Cloud DVR. One neighbor told me he switched his wireless receiver for hte wired version and he's had improved service on the Cloud DVR, but he still has to have the device switched out, he just benefits from now losing recordings now.
I'm almost considering a second DVR to transition new recordings while I play out the old recordings on the existing box, but in a year or so the same boot issue will start all over again so really until Cox invests in new hardware - unlikely with the cloud solution - it hardly seems worth it.
While typing this, I'm wondering if I unplugged the HDMI cable from the DVR before going to bed if it would prevent the DV from getting stuck in boot during the update....
Good luck.