My 9-month-old has just started doing the same things. She's resisting a little bit at nap time, but I believe that she is just cutting a nap. Until recently, she has taken three naps per day. On the days where I have cut it to two naps she has done way better and really not resisted the nap at all.
She doesn't cry when we put her to bed at all, but for the past few weeks she has been doing the same thing. Granted she has been sick, but also, she has gotten four more teeth in the last month. Technically, only three teeth as the fourth one is coming through now. Usually, she will do this for only two or three nights and then after that she is back to normal.
It is tough though. Last night, she woke up screaming at 11:10 and I had to go in and walk with her for about one hour. After I put her down, she continued to cry every so often, but it wasn't awful like it was. I had to just let her go on for a bit because I knew she was tired. While my husband and I want her to know that we are there if she needs us, we also know that she has to be able to console herself at a certain point.
All that to say, we get her to the point where she is calm and not inconsolable and then let her get herself back to sleep. Now, this doesn't always happen on the first try. Sometimes I walk with her and sing for 30 minutes then put her down and if she cries for the next five or ten minutes straight then I go back in and do the same thing, but if you put him down and he isn't crying inconsolably then maybe just try letting him cry off and on and then going back or he will put himself to sleep. Oh..and I also put a teething ring in with my daughter when I lay her back down for the final time.
Hopefully this helps. You know your baby though so this may or may not work for him, but just thought I would let you know that you are not alone and this too shall pass!
I noticed below that one of the people mentioned sleep training. We did sleep training at around 7 months and used the Ferber method. When I said that she goes back to normal after a few nights of waking up, I meant to sleeping from 7 p.m. to around 5:45 when she nurses (she goes back down after that) and then sleeps until about 6:30 or 7 a.m. If he's not going back to that or if it seems more like habit than anything then I don't know if I would recommend picking him up. I am picking my daughter up because we have gone through sleep training and I know that she is in pain/teething and at one point was sick. If after this tooth she doesn't go back to normal then we will be back at square one and start sleep training again. Anyway, just wanted to let you know that if you've done it and he's not teething or whatever then you might just need to repeat the process.