I am "in the process of signing up to cryonics". I will "predictably be signed up to cryonics in the future". I am not signed up to cryonics. It is said apocryphically that more people have died thinking they'll eventually get around to cryonics than have actually been cryopreserved; these are some things I could do to not be among them.
What's actually preventing you? If I was going to this, my approach would be:
Read the website and decide YES/NO whether you want to do it (DONE - I have already learned enough from casual reading. Reading will benefit me no more)
Call the cryonics company up and ask what I need to do. I predict they'll send me paperwork and also suggest life insurance.
Fill out the paperwork making any unanswerable questions a goal(such as life insurance).
Call up a whole life insurance company and ask what I need to do. I predict they'll ask for a medical checkup. Ask for references to a doctor if needed. Add the cryonics company as an interested party so they get notified if you forget to pay.
Call the doctor and ask what I need to do. I predict they'll schedule an appointment.
Leave the house on day of appointment with a plan to get to the doctor's office.
Wait until you get a response back from doctor and send it to insurance.
Wait until you get a response back from insurance and put policy-id or copies of the paperwork on the cryonics application.
Send the cryonics application in and wait for response.
Call the cryonics company and ask if they need anything at all past this.
I'm being very detailed here because I've seen you talk about "executive dysfunction" before, but "dial a number on a phone" really should not be that hard. I like to make a Google doc with the questions I'm going to ask, but that shouldn't take more than 30 minutes of prep. Only step 5 really costs you anything, too.
Since you can, at any time, do the next approximate step on this list, there should be no reason to plan or delay.