I have a loooooong sleeping bag, which I leave in the cot with the end tucked under the mattress, and I zip DD into it when I put her in the cot. She seems to settle to sleep much faster if she can't move around. Not for everyone (my sister, mother of 2, can't believe I confine DD like this!), but it works for us. And it's particularly useful if we're away from home and I put her down for a sleep in the portacot. She's been crawling since just before 7 months but even before that was doing the same as your LO, moving all around the cot, banging her head etc.