Being mindful sitting/working on a computer I find being mindful while sitting on a computer very hard. 

Most movements with mouse/keyboard are happening so fast and intuitive that it's very hard to be conscious of what the actual intention (by clicking on/typing this or that) is; often this also leads me into restlessness or loosing track of time;

I'm sure this is a common phenomenon. Are there certain tricks/tips by which one can be more aware while sitting/working on a computer?
I find being mindful while sitting on a computer very hard.


Being mindful of what you are going is good but not always the right mindfulness. 

What you can pratice in such a situation:


Mindfulness of posture by looking at the touch of the body with the chair and clothes
Sensations that arise in the body and mind



  Most movements with mouse/keyboard are happening so fast and intuitive that it's very hard to be conscious of what the actual intention (by clicking on/typing this or that) is; often this also leads me into restlessness or loosing track of time;


Intention does not matter if it is hard to keep track of initially. Just concentrate on the sensations that arise. Sometimes when you cannot fix a piece of code or perhaps under pressure then these situations also give sensations. Be mindful of them.


  I'm sure this is a common phenomenon. Are there certain tricks/tips by which one can be more aware while sitting/working on a computer?


Takes the whole body or the body as part by part and direct your attention to these parts. Initially when you feel a sensation on some part more on. When you can feel sensations throughout the body then they to divide and dicest the sensations to see them at more lower level of granularity.

Since you are seated mostly be mindful of your posture and sensations it brings. Once you have been in one posture for some time you might get a urge to more. Look at these sensation. Also the texture of your cloths touching you. The touch of the atmosphere on the exposed parts of your body. Heat of cold or the environment you work in and perhaps perspiration running down your body if you perspire. And also the touch of the chair. Touch of the keys when your fingers hit the keyboard.