I think it is very important in life that you enjoy the work you do - whatever that work is, and if you don't, then move on.
I have instinctively known when to move on with my life, and I have almost never woken up with the thought "oh no, I've got to go to work" - I changed careers and retrained about halfway through and have always enjoyed going to work.
Unless you
have to work in a job you don't like for reasons of income or circumstance, I would move on. Several caveates however:
Write two columns on a sheet of A4; Pros in one column, Cons in the other. What you like about your current job, what you hate about it. This will help you decide.
Do you really hate your current job, or just a couple of aspects of it? I look back and think 'at the time XYZ really annoyed me', but actually, the rest of the job was fine. All jobs have downsides. When you are a bit down in the dumps, the downsides can assume large proportions. But be careful not to give up a good job for a few niggles.
Do not resign your current job until you have a new firm offer. It is much easier to get a new job while you still have a job.
Going from shift work to 9-5 is a big change. I have worked shifts most of my life and prefer it. I worked 9-5 a couple of times for 6 months each. Yes, you can order your life better. When your friends ask you to Christmas this year, you can say yes without having to wait to see your roster. You can play squash every Tuesday evening; go to the pub every Friday. You have all your weekends and Bank holidays off.
But, you are doing the same job day in, day out. You travel in the rush hour twice a day, every week day. Finding a parking place is difficult because everyone else is at work. You have to do your shopping at the same times as most other people - shops will be busy at those times.
Perhaps a change of base is feasible in your current job? Same company but different surroundings and different local boss might be all you need to refresh you. Or go for promotion within your current company or move sideways into a different area?
If you do decide to retrain then go for it. But be aware that it could be a LOT of work. You must factor in how you would study, where you would study, and how you will pay the mortgage and run the house and cars while you are studying.
Good luck !
PS, if you have the savings and no kids, now might be a good time to travel and see the World. (Covid allowing, obviously). Companies usually offer extended (unpaid) leave. See what your HR department offers. A long break of a couple of months travelling might be what you need to recharge.