OSX Boot Manager and Mac Partition Extremely Laggy

I have an A1502 MBP with Boot Camp and Windows 10. I use my W10 partition the vast majority of the time. When I want to switch, I would hold the option key at boot for a few short seconds, and then I can pick. Lately, I have to hold the option key for almost a minute. Then after the boot manager finally loads, my input via keyboard or mouse is only effective every 5-7 seconds, for only 1 second. If I choose the windows partition, it boots (although not speedy) and works fine. If I choose the mac partition, it takes a long time to boot, and I am left with the same issues with mouse and keyboard response. The screen lags right along with the input. It's basically impossible to even log in. A PRAM reset will correct this temporarily, and it boots right into the Mac without having to use the option key. But If I try to switch back to Windows, it happens all over again. I need to reset the PRAM in order to boot back into the Mac side. Any suggestions?