I will be having 2 years work ex in september 2023. Should i resign at that time to fully focus on CAT for 2 months? Will it affect my chances in the interview?

CAT is a highly unpredictable exam. I would strongly recommend you to not quit your job for attempting CAT.

Even if you dedicate suitable hours on weekends you wont have any problems with clearing the paper since there is alot of time for CAT 2023. Start your prep if the job gets in the way then decide whether to resign or not IMO :)

Check with your employer if they can provide you leave without pay.