DS is 18 weeks. For the last week or two, he has started to wake up about 45 minutes after going to sleep at bedtime. This suggests to me that he thinks he's having a nap rather than a night's sleep, since 45 mins is a nap sleep cycle (I think night time cycles are longer IIRC).
We have a bedtime routine which hasn't changed in the last month. Bedtime is always between 6 and 7pm, although the exact time depends on when his last nap finished, so that he's not too overtired at bedtime, (or we have a fight on our hands).
The room is much darker at night than for naps. At night he sleeps on a mattress next to mine, but for naps he sleeps in a carry cot. For naps, I rock or feed him to drowsiness in a chair, but at bedtime I feed him in bed. So he should be able to tell the difference.
Has anyone else's DC done this? Did they just stop? Is there anything I can try to help him stay asleep once he goes down for the night?
He did use to sleep for a good long stretch at the beginning of the night - in fact, his best was 10-11 hours without waking . But now he struggles to sleep for more than 3 or 4 hours after bedtime before waking. I'm wondering whether there might be a connection, perhaps? He can't self-settle yet.