Thank you guys for the replies!
I’ve actually read that linked wiki article in the first place but somehow missed “flickering” part in troubleshooting section. That gave me additional thoughts to double check how Redshift is actually started. Turns out Redshift shortcut inside Whisker menu had redshift-gtk command and what I added (as already mentioned) in Application Autostart was just redshift. So after updating it to redshift-gtk everything seems to work as it should. For now at least.
Oh and thanks for pointing out Gummy - if Redshift will start giving me additional problems, I’ll make sure to check it out as well.
One last question: in Application autostart I found “Geoclue Demo agent” - is it still needed since Redshift gets location from manually added coordinates? Is it safe to disable it? It slightly bothers me to have things in autostart which potentially are not used by anything else 