Sometimes I use the 10-minute timer approach. (This works for housework as well!) Set the timer for 10 minutes and promise yourself you can get up and do something else when the timer goes off. Usually by the time the timer goes off I am in the middle of something and interested enough to finish it. Often I will reset the timer for 10 more minutes. Occasionally I have gone an hour or two because I have gotten motivated. Rarely I will stop at that first 10 minutes.
For me, getting started is the biggest hurdle. Once I am into something for 10 minutes, I can often go on without boredom or mental discomfort......