Kathryn gives excellent advice!
The only thing I have to add is that short napping is very common at this age. They start having a different REM/non-REM pattern, and they have to learn all over again how to transition through the different sleep phases. A lot of times we have to re-teach them how to. What I ended up doing is holding my son through the jolts at the 30-45 minute mark. I spent a day watching him sleep (which didn't take long since his naps were all less than 45 minutes!
), so I could see when he was starting to stir. Then, I would make sure to go up there BEFORE the stirring happened, and I would hold his little arms/legs down thru the jolts (he was still swaddled then too). Eventually what happened is he was able to transition himself! I was really worried I would become a prop by doing this, but I think it just helped him to learn to make that transition all by himself. I got this idea from this website, so I know it is BW friendly!
A warning: the first few times you try this, you might not be successful and your LO may wake up all the way. My policy at that point was to do whatever I could to get him back to sleep, to keep overtiredness from becoming another issue we had to deal with. Since they nap so frequently at this age, it really doesn't take long to re-train them. By the 3rd day, my LO was starting to transition on his own, at by the end of a week I didn't even hear him stir at the 30 minute mark anymore. You just have to be consistent, and be prepared to lose some "Y" time for a little while. I was in tears by the 3rd day, but miraculously, that's when he started improving, and things got better fast after that. It was so delicious to have back those 2 hours of "Y" time when it was all over! And after this learning phase, he briefly had 30 minute naps periodically, but in every instance it was simply a matter of extending A time to fix it. He had learned how to make those transitions, and never forgot how to after that.
Hope that helps!