Hello Alana,
Yes my first guess was also application Pool shutdown and wakeup. Thats not the problem as the website will stay slow all the time. Also its reproducable that two browsers on the same machine work with completly different speed.
I will provide logs of the page you mentioned when i run in that problem again. Clearing cache did reproducable solve the problem. Of course the first call might take a second longer, but after that it works fine.
Best Regards
Dario