Slow performance on new MacBook Pro M3 48GB RAM

What is "VPN"?

I'm not trying to contradict the previous suggestion. All of that is most certainly correct. It's just that VPN functionality has proven to be a very successful strategy to get scam software installed.

What I mean is that whatever is causing the problem on your computer probably isn't the VPN functionality itself. The problem is here:

i did transfer data from my old intel mac to this new apple M3 (dont know if this is the cause as i checked all apps are as per apple chips).

I don't know what you mean with that second part. But most likely, you have one or two dozen 3rd party system modification apps installed on that old computer. They probably aren't compatible with the new computer.

Apple updates the operating system every year. On top of that, Apple recently switch the entire system over to a new processor chip. These scam apps aren't interested in updating old apps. Once they've got your money, they're done with you. Those that are most successful and still in business may update their software just so they can keep collecting that $49.99 monthly subscription. But they don't actually improve anything. They slow your computer down. They want you to think that you need more "clean up", "tune up", or "speed up" apps.

And don't even get me started on 3rd party "security" or "privacy" apps. They give you neither. But they are closely related to the "clean up" and "tune up" industry.

Unfortunately, what this means is that you'll likely have to erase your new computer hard drive and reinstall the operating system. You can restore from backup, but when you restore, this time make sure to avoid restoring any software, apps, system settings, or "other files". You can manually reinstall only the 3rd party apps that you simply can't live without. Any kind of software mentioned in this thread is something that you can definitely live without.

erAdnan wrote:

i am using only VPN. but same VPN is being installed on other Macbooks(we have few more macs of same config) of same configuration. other macbooks are working fine as expected. have issue with 1 mac only for now. so VPN doesnt seems be a cause.

In addition to the excellent advice provided by Garnt-Bennet-Alder, post an etrecheck report so that we can see if anything else is impacting your computer's performance. Using EtreCheck - Apple Community

A virtual private network, or VPN, is a private connection over the Internet from a device to a specific network.  VPN technology is widely used in corporate environments. If you need to be "present" on an institutional network, a VPN is a great tool for accomplishing this. it is generally issued and controlled by the institution.

Almost all other uses are a SCAM. There is generally no need for you to have a private connection to a VPN vendor's Network, except to make it easier for them to harvest your data to sell.

If VPN vendors just stopped there, it would be bad. But many of these packages also insist on scanning all your files, non-stop, -- nominally looking for viruses, but who knows for sure what data they are harvesting. Their non-stop file reading punishes your computer's performance in the process.

Some also break into your other secure connections so they can be FIRST to examine your data, often leaving your Mac MORE vulnerable to attack.

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners, Bit Torrent, or a VPN that you installed yourself. 

¿Are you running anything like that?