high cpu consumption? How to solve?

I install and activate spirit theme, however, it sometimes can be load by browser and sometime not (without much edit of original look). I ask this to the hosting service provider and below comment was given.

It is your wordpress plugin & theme issue, it is consume very high of cpu usage which causing your page doesn't completely load.

Try to disable all your plugins & switch to other theme first to find out which plugin or theme causing the problem. Please check this with your web developer to optimize your website.

Please advise thanks.