Make it fun (going outside, listening to music, playing: dogs are great for this), incorporate exercise into as many daily activities as you can, and above all, eat healthy for the energy and nutrients you'll need to keep you motivated.

I am a gym rat at heart so not sure how much I can help. Liked what @SteveB said about workout buddies. Right now have 3 young guys at my gym who are super motivated about bodybuilding and ask me for a lot of training advice just cause I've been involved in strength training and physique development for decades. Their motivation and hunger inspire me to drag my beat-up old body into the gym. Because others see me helping these guys I get approached at least 1-3 times every workout asking for advice and I love it. Not because I crave the attention but because it's so nice to share my knowledge and passion with those who are truly interested. Maybe look for that? Find someone who is passionate AND positive who you can feed off of and be inspired by and not someone who is just going through the motions or is just there for the socialising. If you need to change things up once in awhile go for it. Like I said I'm a gym rat so I know not everyone has my perspective and drive but if you ever need some advice or a kick in the ass feel free to message me. Peace!

Even if I don't feel like a workout I go anyway. A light workout is better than no workout at all. Unless I'm just overworked I'll do a light workout even if it's just 15 min. You'll feel better and sleep better too.

Sounds like the routine might be a bit of a drag. I make small changes to mine every 3 to 4 weeks. Do you follow a progression in your weight training? The first month as stability/endurance, second month as muscle growth/hypertrophy, the third as strength, the fourth as power. Changing resistance, grips, number of sets and reps, ext.

I think about all the positive effects of exercise. The positive effects are numerous and there are just too many to discount or overlook. Exercise is about the most positive thing you can do for your physical and mental health. There is no better way to spend 30-45 min a day than exercise. period.

That is how I motivate myself when I start wondering why I do it ,

I draw motivation from different sources, but mostly it's three things:

1. I was diagnosed as pre-diabetic a few years ago. My doctor at the time scared the shit out of me by providing me with a packet of info that talked about diet, exercise, and losing weight. I'm medicated for a few things already and have no desire to become an insulin-dependent diabetic. Don't feel I fall into the weight-loss needed category, but I could do more to help prevent it diet-wise. Exercising is something I am already setup to do at home.
2. I see other men my age who clearly do not exercise, and it shows. They look older, and fatter than I do. No thanks!
3. Fast results. When I am on my routine, I can see and feel changes in my body. That "instant" gratification is a great motivator.

I am working toward a reward for myself. When I hit one year I am going to plan a weekend at a hot spring! The big thing I am finding is being kind to yourself. If something happens and you miss a day or two just get back on the horse(so to say)and go. Working out right after work has worked out best for me.
Good luck and go get'em evestrat!