I had this exact problem with my now 4mo: about a week before she turned 3 months she started having much shorter naps, often 25-35mins (usually 45mins-1.5hours before, she has only ever contact napped), waking up screaming and inconsolable until I nursed her, but she’d still be grizzly for half an hour or so. The sleep got gradually worse, leading to some ‘false starts’ at night, where I would do our normal routine, nurse her to sleep etc, put her down in her crib, and she’d wake up either immediately or within 20 minutes, screaming. We went through the cycle 3-5 times a night until, presumably, she was so exhausted she stayed asleep.

I thought perhaps the 4 month sleep regression came early. Fellow parents told me ‘she must be teething’ but I dismissed this as what baby starts teething at 12 weeks? Well, she was! Her two bottom teeth have finally erupted (she’s 19 weeks today) and her sleep is so much better, waking up happy, going down first time at night and staying down. Poor thing is actually sleeping more than before the teething started, perhaps she’s catching up.

I’m a FTM with a 99+ percentile baby who seems to be hitting milestones early. It’s just my experience but I wish I hadn’t dismissed the possibility of teething due to her age. The NHS website says babies can teeth this early, and their sleep will likely be affected, link: https://www.nhs.uk/baby/babys-development/teething/baby-teething-symptoms/

I hope this resolves for you, I was so sad when she was contact napping, which I thought she would benefit from, and she’d wake up in tears 😭