There's a lot of factors that could cause your issue. But the usual culprits to check first are: theme, plugins, image sizes, etc and a big one is hosting. Have you run a actual website speed test to see what could be the cause? Use
https://gtmetrix.com/ as it will give you tons of info about is affecting your website speed. No need to jump to CDN, speed/cache plugins or VPS until you have fixed the underlying issues.
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