@Muru the different results with every refresh are normal. It is likely because of one or multiple things:
1. You have a caching plugin like litespeed, wp rocket, wp fastest cache, etc
2. You're using a CDN like Cloudflare to serve URLs
3. Your hosting service is automatically caching pages to reduce load
Either way, you can consider the first page load results as accurate. If the second page speed test results are better, your caching is working well. If they drop, that's when you should check what's going wrong.
Also, some other page speed services
• gtmetrix
• pingdom