3 month old fights falling asleep

For the last couple weeks, my son has grown a habit of crying his lungs out the moment he starts falling asleep.

He literally fights tooth and nail for 10, 20, even 30 minutes. Sometimes I get frustrated so I have to put him down, drink some water and collect myself for a few moments and try again.

He gets enough sleep in; doesn’t stay awake longer than he needs to so it shouldn’t be overtiredness. Gets between 12-14 hours of sleep a day on average which includes his naps throughout the day.

I thought it was gas, but it hasn’t been the case.

Nighttime routine is pretty solid; we have bath time, story time, nighttime feeding, tummy massage and cuddles. I dim the lights in the room around 6pm or around the time there’s a sunset. Naps are also in his crib with the curtains undrawn. I also have a rule in the home that after bathtime it’s quiet time. Wind down time. So no loud noises, no electronics used in the room unless it’s his lullabies - which the device is hidden so he can’t see it.

*Tried to swaddle him a couple times and he hates it. He cries bloody murder.*

I’m stuck as to what is going on. His next leap (wonder week) isn’t until the next 2 weeks I think. Is it just a phase? What is causing this? I’m so confused and want to fix it so he can rest faster and in a more comfortable and relaxing state.

Thank you to anyone able to give suggestions, advice and tips.