Every household has two or three jobs that have been pending for months. The loft. The cupboard under the stairs. The box of cables. They are not hard and they are not urgent, which is exactly why they survive: nothing forces them, and each time they are considered they feel vaguely enormous.
The common thread is that the job has no defined beginning. "Sort the loft" is a description of a finished state, not an instruction, so there is nothing to actually do when you have a spare hour.
Name the first physical action
Not the plan, the action. "Carry the three boxes nearest the hatch down to the landing." That is specific, takes four minutes, and once it is done the job has started, which turns out to be most of the difficulty.
If you cannot name the first action in a few words, the job is too large to be one job and needs splitting before it needs doing.
Give it a container of time, not a target
Half an hour on the cupboard, stopping when the half hour is up regardless of the state it is in. Deciding instead to finish it guarantees it never starts, because finishing is unbounded and nobody has an unbounded afternoon.
The state it is left in can be worse than before, and that is acceptable. It is a job in progress rather than a job avoided.
Deal with the real obstacle separately
Quite often the job is blocked by one specific thing: nowhere to put the thing that has to come out, no bin bags, a tip run that needs a car, a decision about something sentimental. The job is not stalled, the obstacle is. Identifying it and clearing just that is a far better use of twenty minutes than another attempt at the whole thing.
Accept a worse temporary state
Most of these jobs get uglier in the middle. A hall full of boxes for two days is the normal condition of a loft being sorted, and people who need the house presentable throughout cannot start. Pick a window where some mess is tolerable and say out loud to whoever else lives there that it will look bad until Sunday.
Stop making it a milestone
Jobs that sit for a year often acquire significance they do not deserve, and then they need the right mood, the right weekend and a clear run. They do not. Doing a quarter of it badly on a wet Tuesday evening is worth more than another six months of waiting for the proper occasion, and after the first quarter the thing usually loses its weight entirely.