Hello and welcome to BW forums
There are different methods of W2S depending on the age of your baby and what works best for him. In case you haven't seen this I'll link it:
How do I address habitual wakings? (wake-to-sleep and other methods)For your LO I would recommend the method (naps option 1 in the link) where you go in and begin shush/pat at 30 mins to help him get through the transition between sleep cycles. You might need to continue for 20 mins until he is again in deep sleep before stopping. The idea is to help before he fully wakes, it is often easier to extend the nap with a LO who is still sleepy, and at the same time remind LO that he is supposed to take a longer nap rather than wake up.
You might find you need to do a few rounds of this. Try 3 days then hold off day 4 and see what happens. If he wakes you need to try to resettle him again and then continue another round of W2S for the next 3 days, hold off again the next day. This gives you a chance to see what happens as W2S is not intended to become a prop.
The method where you disturb LO to kick start a new cycle is generally more useful for older LOs.
Whilst I'm here I will mention that if naps have suddenly gone shorter it can be he is ready for a longer Activity time. Here is a guide for A times, every LO is different of course this is only guidance:
Average A times- BOOKMARK ME! It may be that you are running on a 1hr or 1hr 15 min A time when LO is ready for 1hr 20 or 1hr 30. The slightly longer A time can help him to be tired enough to transition alone again.
I hope this helps. Please let us know how you get on