Me again. We had real problems with overtiredness back in the days when DS used to be a poor napper. (Note the past tense & take heart. :))
He?d often be awake all evening until late. At around 6 months, he?d wake maybe 2 or 3 times a night. During a week?s holiday when naps were completely hit & miss (often miss) he got seriously overtired and started waking 6 or 7 times a night and had to be fed back to sleep each time, and was up for 1.5 hours at least every other night, which carried on for several weeks afterwards. He?d not nap in the pushchair, car or sling, and would only feed to sleep, and I couldn?t put him down without him waking and refusing to go back off.
I managed to sort his night time sleep at around 7 months using some NCSS / PUPD ideas ? after that, he?d wake briefly 45 mins after going to sleep, and then once for a feed around 4am. It only worked due to getting the naps right first though.
I had a week where I did nothing but get him to nap. He?d feed to sleep and I?d sit with him on my lap. Rather than trying to follow his tired signs, I tried for naps at 9am and 1pm (he woke at 6.30am) which seemed to suit him. After he?d had several days of better naps, I was able to put him down in the cot once he was asleep and pat him when he twitched (he woke otherwise). Within a few days I didn?t need to pat him any more. The night-time improvement was much faster than I expected ? as soon as he was having a morning nap and a long lunchtime one, the long periods awake at night disappeared.
I think the effect of overtiredness is similar to CarGirl?s DD?s problem ? the longer babies are awake, the more stress hormone they produce. Naps bring down the cortisol levels but if they don?t nap, the body produces adrenaline to keep them going. Unfortunately it makes them fight going to sleep, wake more frequently (often at the end of every sleep cycle), be wide awake in the middle of the night and want to be up early in the morning.
At 7 months I reckon your DD probably needs 3 naps a day. Especially if she?s overtired, she probably can?t be awake much more than 2 hours before needing another nap. It?s worth trying to focus on getting her to take the first nap - it?s supposed to be easiest to fall asleep for this one as they?re relatively better rested after the night. I?m sure you will have to hold onto her to get her to stay asleep but if there?s any way you can do that, it?ll be worth it IMO.
Having a consistent wake-up time helps. Exposure to daylight on waking helps set their biological clock. Trying for naps at relatively consistent times often helps too.
The times when you?re likely to be in the car sound like good nap times to start with. Around 9am and around 1pm are times of the day when it?s easiet for babies to fall asleep & stay asleep. It?s more important to watch your baby?s signs & avoid overtiredness than to get them sleeping at the ?right? time though. If a nap is missed, it?s best to keep your baby awake and go to the next sleep period (day or night) but make it a bit earlier.
If she does manage to sleep in the car, that?d be ideal as babies learn to go to sleep most easily when you use the same method to get them to sleep for all naps.
The earlier the bedtime the better for an easily overtired baby. If having a late afternoon nap means that bedtime is late (later than 8pm, say) then ditch that nap and bring bedtime forward by as much as necessary. In general, an earlier bedtime often means a better night?s sleep. Some books recommend bedtimes as early as 6pm if your baby is able to sleep then.
Dunno if any of that helps. If I think of anything else, I?ll pop back.