I always exercise first thing in the morning . Otherwise my day gets going and I struggle to find the time. On waking , the hormone cortisol is naturally released to help you get out of bed and get going. I usually have a cuppa first thing and walk around to waken my body up and then I do my movement / exercise of the day.
By scheduling into my diary my workout I know it will get done. You do not have to spend a long time doing it. My regular strength and conditionning workout is 45 minutes , my pilates 55 minutes but if i am short on time I make sure I do 20 minutes. So start small. Start with small manageable workouts of low intensity and then you can increase the time and intensity slowly over time as your fitness improves.
Be consistent. Little and often is best. Make it part of your day and take every opportunity to move throughout the day. Walk where you can and take the stairs as often as possible.
Mix it up. Vary your routine by trying different types of exercise. I lift weights, run and do pilates and yoga but on different days. That keeps it interesting but also gives my body variety and helps me to avoid injury but avoiding overloading the same body parts. Strength training will target muscles that support your body for running. Running is more cardiovascular and thus mixing it up targets different areas of the body and different aspects of fitness.
Pay attention to your body during and after exercise. If your are feeling tired after a poor night's sleep then maybe do some gentle pilates or yoga type exercise and leave the strength training for another day. Listen to your body. Pushing yourself too hard can lead to over stressing the body and end up in injury or burnout.
Stay motivated by goal setting or setting a challenge with a friend. If you like exercising with a friend then that can help with the motivation or commit to a class. Personally, I stay motivated by just making exercise part of my day and I know I just have to do it, so I do. I usually rest up on Sundays or will take things gently. As I usually garden on the weekend I use gardening as my exercise for the day.
Ultimately, by making exercise part of a daily routine requires making it a priority in your life. By recognising the importance of regular physical activity for your overall health and well being makes it non negotiable and an important part of your life.