Observing sensations during normal time. I observe very strong sensations even post meditation. They are strong at some time and some time subtle. I am alternating between apanana and vipasana. I would like to understand why they are so strong at times.
The experiences are based on the sum total of your past fabrications and what has surfaced in a given time.

In the different times the fabrications that has surfaced are different hence the diversity of the experience.

Dwelling on matters like this will inevitably make you crave or be averse to some types of sensation hence regress in your pratice. You should just be aware regardless of if it is strong or not.

Having said this some times the strong sensations can be due to rapture.