Try using game booster or closing programs in the background.
Try turning off any extra programs that take up extra ram. It used to happen with me as well and I lagged really hard but I figured out that it was Google Chrome, and Frostwire (Limewire basically) running in the background.
You client may not be loading propperly at the beggining, then after a while everything is ready, thats when you can start playing fine :S
What are your computer specs?
Fully defrag ur hard drive ,Close all unwanted back ground processes ,fully clean ur Pc with Pro anti Viru/Spy way program .
Use CCleaner or as Lil wayne siad defrag your computer.