With my iMac, USB wireless mouse gets laggy for while. How do I fix it?

My late 2013 27 iMac connects to external monitor by Thunderbolt, using external SSD for boot, external hard drive via both USB. I use Bluetooth keyboard. Also, my Logitech M325C, first I plugged in USB unifying receiver, it was smooth but an hour or two later, it gets laggy. I usually use external USB cable and it works fine as well. What could cause it? How could I fix it?