A good warm up exercise to rev up your hand eye coordination and free your mind ready for Drawing is to draw wire.
Take a piece of garden wire or even string and place it on a plain surface.
Draw what you see. Start with quick fire immediate mark making. Responding intuitively to the shapes. After each Drawing move the wire to a different bit of the paper surface or remodel it.
After five minutes actual drawing time start taking longer begin to notice the detail. Add in the smaller irregularities, notice the light and shade as one wire crosses another, describe the shadows it casts.
Take some time to draw with your non writing hand and observe how much more carefully you observe and translate what you see. Try to do the same thing when using your writing hand.
When you get bored take a moment to settle yourself and then gently push yourself to continue fir, say, another five minutes. Or, if you want to really benefit, ask your self to stay with it for longer. The only rule would be that whatever time scale you set stick to it. It’s surprising how you can change your focus and really drill down if you set yourself a goal.