Blank display after startup and Idle time (Ubuntu 20.04)

This weird issue just started. I'm running Ubuntu 20.04 with a GTX 1070 GPU. When the idle timer kicks in and disables the video signal, it doesn't reactivate when I move the mouse or press a key. The led on the display turns on for a second and the screen flashes "no signal" before shutting off again. If I continue moving the mouse around, this will happen repeatedly--display turns on, flashes "no signal," then turns off again. The only way I can get the signal back is to disconnect and reconnect the HDMI cable. When I tried rebooting, I noticed this same behavior occurs immediately after startup. It's like whatever process normally triggers the video output to activate is getting interrupted.

I've tried switching between different driver versions and rebooting but it doesn't seem to make a difference. Not sure what I might've changed to trigger this behavior. I think I installed some updates last night (nothing major, just the usual security patches/minor application updates).

Below is the output from nvidia-smi command:

Wed Aug 11 19:45:51 2021
+---------------------------------------------+ | NVIDIA-SMI 470.57.02 Driver Version: 470.57.02 CUDA Version: 11.4 | |-------------------------------+----------------------+----------------------+ | GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC | | Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. | | |
| MIG M. | |===============================+======================+======================| | 0 NVIDIA GeForce ... Off | 00000000:0B:00.0 On |
N/A | | 0% 48C P8 12W / 151W | 463MiB / 8116MiB | 0% Default | | | |
N/A | +-------------------------------+----------------------+----------------------+

+---------------------------------------------+ | Processes:
| | GPU GI CI PID Type Process name
GPU Memory | | ID ID
Usage | |=============================================================================| | 0 N/A N/A 1703 G /usr/lib/xorg/Xorg
234MiB | | 0 N/A N/A 1977 G /usr/bin/kwin_x11
77MiB | | 0 N/A N/A 1986 G /usr/bin/plasmashell
65MiB | | 0 N/A N/A 2453 G
...akonadi_archivemail_agent 3MiB | | 0 N/A N/A 2560 G .../akonadi_mailfilter_agent 3MiB | | 0 N/A N/A
2574 G ...n/akonadi_sendlater_agent 3MiB | | 0 N/A N/A 2578 G ...nadi_unifiedmailbox_agent 3MiB | |
0 N/A N/A 3072 G ...mviewer/tv_bin/TeamViewer
2MiB | | 0 N/A N/A 3313 G ...AAAAAAAAA= --shared-files 43MiB | | 0 N/A N/A 9182 G /usr/bin/systemsettings5 18MiB | +---------------------------------------------+

I've got also a blank display after the idle time kicks in. However, in my case this issue began as soon as I switched from the Ubuntu standard graphics driver (nouveau) to the proprietary NVidia driver (5xy). The video signal doesn't turn on again when using the mouse or keyboard. Thank you for the workaround of disconnecting and reconnecting the HDMI cable, this activates the video signal again.

GPU: GTX 1030

This solution seems to work so far for me (see link below): Disable C-State (try one parameter at the time to ensure you disable only what is needed) in the BIOS in CPU options which refers to idling the video signal (terminology and location varies depending on your BIOS version and manufacturer).

NVidia: Ubuntu 20.04 freeze on idle when connected to HDMI