Is this just a phase?

LO has started some phase within the last couple of weeks where when we try to put her down at night, she just fusses for what seems like an eternity before she will go to sleep. We haven't changed anything about her bedtime routine. She hasn't been a super solid night sleeper all the time (maybe like 70% of the time) but she never really had any issues going down at first. Is this just a phase? Anyone else go through this? She's been sleep trained for months...