Tips

A few things that can help get you unstuck - an extract from my general 'inertia' post.

Schedules

Often when something is in a regular schedule, inertia applies more to the schedule than to the individual task - the tasks within a regular routine are more likely to get done. Be careful not to over-focus on the act of scheduling rather than doing things.

Start off easy

Choose a task which is not a major issue. Make it as easy as possible to accomplish by taking account of any sensory issues and breaking down the task into manageable pieces. Try not to make a big deal about it or apply a lot of pressure.

Shock

Some people may need to be shoved rather than prodded in order to change focus. Alarms or timers can help for this purpose. Other people, such as irate parents or partners, are good at "shock therapy". It is probably not healthy to be shocked often (besides which, the shock value would likely wear off), but for the really important things it may be the only reliable method.

Set a timer

Aside from the schedule and shock values of a timer or alarm, it can help to know that one task does not go on forever. Timers can help with transitions by giving your brain time to get used to the idea of changing focus. Timers can also work for limiting unpleasant tasks. If you know you only have to do something you don't want to do for a specific amount of time, then it may be easier to get over the initial resistance. Timers can also help prevent exhaustion from doing a single task for too long.

Accompaniment

Sometimes it is impossible to get things done while being 'watched' by another person. It may be best not to tell anyone else so you don't have to be accountable to anyone. On the other hand, some people find it easier to get things done if there is another person around. The other person may need to be occupied, or it may be okay if the other just sits there.

Rewards

Having rewards for the completion of certain tasks is helpful for some people. Rewards may not work for long, but may help for getting started into a routine. A good reward has to be not too difficult to achieve, immediate (at least initially), and highly desired but not irresistible. Rewards do not have to be par of an elaborate schedule or earning scheme, they can be made up on the spot. Punishments usually don't work and can be de-motivating. If you use rewards, don't back down. Delay the reward until the decided task is completed. You can have what you want - as soon as you're done.

Listen to yourself

If something doesn't work or stops working, change. Also try to listen to your body and your feelings when they tell you that you need to be doing something like eating or sleeping. Feelings of pain are a message that something is wrong and needs to be changed.

Use your motivation

Pushing on inertial tendencies will usually just cause them to push back. It is more important to do things that you understand the reasons and have the motivation to do.

Don't nag

Nagging (repeated, annoying, or unnecessary reminders) is likely to cause resistance to any of the strategies you may try to implement. An occasional reminder by someone else may help you stay on task, but these need to be carefully suited to your own difficulties and desires.

Medical treatment

If you have any physical or mental illness which causes lethargy, it needs to be treated before you can make much progress. Take all prescribed medications and investigate the possibility of any treatable illness.
Stop trying: If you really can't get started, do something else. Try doing something completely different, but not something that you are likely to get "stuck in". Don't forget to try the task again later.

Ease transitions

Allow a short, specific amount of time or other limitation (e.g. 3 more pages of reading) before changing tasks.
Use transitions: Catch yourself in transition times so you don't have to stop doing one thing in order to do what you are trying to accomplish. (e.g. Start a sink full of dishes when you get up to get a drink.)
Break it down: Try to break down the task into manageable pieces.