Have you tried approaching it with the idea that you don’t have to form a stable routine? The next time you’re sitting around with >20 minutes to kill, go for a run instead of doing social media/HN/Netflix/whatever it is you might do to kill time. If you found you woke up an hour early and can’t get back to sleep, go for a run. Maybe it’ll eventually lead to a routine, but maybe it won’t and that’s fine, too, you’re not trying to win a marathon. Running once is better than never, so no need to put pressure on yourself to form a stable routine.