Hi! I have a Lumia 735, and I had the same issue than you have.
I believe that it happens because something went wrong during the installation. The first time I installed the last build of W10 I didn't know about that issue, of waiting for like 10 minutes in the lockscreen after installing, so i restart my phone a lot of times untill i search on web
Due to that, my phone got very stupid so i did it again, I use Recovery Tool and reset my phone and then install W10 again without even touching the device during all process, and now it's everything ok.
Have in attention, that if you have a lot of apps it will take longer and I believe it also damage the SO. The best thing is to reset your phone and install W10 and then install the apps you need.
I hope i helped you. Be noticed that Lumia 730 and Lumia 735 its practical the same thing.