I Am Up For / Starting Badly On Purpose
Lower The Entry Until Beginning Is Trivial
If starting requires a decision each time, it will not survive a difficult week. Make it require nothing.
The usual approach is to make the first attempt significant: block out a proper session, clear the day, treat it as an event. This is exactly backwards. A significant first attempt has a high failure cost, which means it gets postponed until conditions are right, and conditions are never right. A trivial first attempt has almost no failure cost, which means it can happen on an ordinary Tuesday when you are tired and slightly unwilling. Trivial attempts survive real life. Significant ones wait politely for a version of your week that is not coming.
Lowering the entry means asking what the smallest possible version of this looks like. Not the smallest useful version, the smallest version full stop. Fifteen minutes. One repetition. Watching for half an hour without participating. Turning up and leaving early. The instinct is to object that this is too little to achieve anything, and the objection is correct and irrelevant. The first weeks are not for achieving anything. They are for establishing that this is a thing you do, which is a different task with different requirements, and it is served by frequency rather than duration.
There is a secondary benefit. When the entry is low, you stop negotiating with yourself. Most abandoned beginnings die in the negotiation, in the twenty minutes of internal argument about whether tonight is really the night. If the commitment is small enough that arguing about it takes longer than doing it, the argument stops happening. That is the whole mechanism, and it is worth more than any amount of enthusiasm, because enthusiasm is a weather condition and a small commitment is a structure that works in any weather.