It might be a little different than before to wake up after hitting your 45. The rigidity stays a little bit longer, the shoulders can be rounded without any realization, and the lower back can be stiffer in the mornings. Perhaps, rather than jumping directly into hard back exercises, a more relaxed methodology on posture and alignment exercises is easier. Minor but deliberate actions immediately after waking up may sometimes help ease the day. These are exercises that are easy, consistent, and straightforward. They are not like challenging the limits but making the body feel in balance before the day is completely started.
Gentle Neck Lengthening

Raising the head slowly with the chin relaxed and lifting the crown of the head will be beneficial to make a space in the neck. It is able to lessen the urge to stick the head out in front of the screen, which occasionally occurs due to time spent with the books.
Shoulder Roll Reset

The controlled backwards and downward rolling of the shoulders may serve to remind the upper body to be as it is. This is a tiny motion that can be used to stretch the muscles in the morning and relax the chest without imposing anything.
Wall Alignment Check

The posture of the back against the wall with slight rest of heels, hips, and shoulders can provide awareness. It could indicate some posture habits, which are not obvious, and could move the body to a more upright pose gently.
Chest Opening Stretch

Putting the hands behind and raising them a bit could cause some slight strain in the chest. This may offset the forward rounding, which tends to accumulate over the years.
Seated Spine Lift

Sitting erectly and envisioning a rope holding the upper body and pulling upwards may help promote a good posture. Such an awareness activity could be as simple as sitting during the day and feeling supported.
Morning Side Stretch

The extension of one arm up in the air and leaning slightly on the other side may establish length on the torso. This is a relaxing experience and can help to even out uneasy tension.
Hip Flexor Ease

Tight hips may be loosened by taking one foot backward into a light lunge and maintaining the torso in a straight position. In the long run, this may lessen straining the lower back, which occasionally influences alignment.
Ankle and Calf Mobilizer

The lower legs can be stimulated by lifting on the toes and rolling downwards. This movement could be helpful to the ground-up balance and posture.
Scapular Squeeze Hold

Holding the shoulder blades together without raising the shoulders and taking a few seconds could work the supportive muscles. It may be light, yet it may support the stability of the upper back.
Forward Fold Release

A gentle forward bending due to hip flexion, with soft knees, can result in spinal decompression. This may be relaxing and can be used to release stiffness that may be remaining.
Core Breathing Activation

Hands on the abdomen and slow and deep breathing may naturally involve deeper core muscles. Correct breathing may also have a minor but significant role in posture.