Lagging iphone 15 in gaming

im using iphone 15 for 1month and everytime i play games like call of duty i expirience random lag or sudden lag and the only way to fix it is to make my frame rate low then make it max again in settings but mins later it will lag again (or next game) and its so irritating because i thought iphone 15 (my new phone) will not expirience any lag because its latest phone and highest phone as of now. i hope developers fix this.