Your PC's BIOS contains programs that help your computer get started and let the operating system connect with the hardware in your computer. Vendors update the BIOS to fix bugs or enhance performance. BIOS is short for Basic Input Output System.
Changes in the BIOS cause changes to the machine ID, so that's why your machine ID keeps changing. BIOS updates are often more frequent when you get a new PC. The updates should slow down a bit after a few months. Some computers have almost no updates after they're launched. Others, especially Dell computers, seem to have a lot. In emulators, such as on a Mac, BIOS updates may occur on each software update.
For example, in one new computer, there have been 4 updates in three years, which is more reasonable. One of the updates was put out almost 3 years after launch, so you never know if a new BIOS is coming out. Updates support new operating system features as they know users will be updating to newly-release operating system and features that weren't available when the computer was first released. A LOT of people never do BIOS updates, mostly because they're unaware of them, and they're probably ok most of the time. It's probably a good idea to do them, though not always right away. Waiting lets other people test an update out for a while and perhaps any issues with it will get resolved before upgrading to it, in which case a new BIOS version is released shortly thereafter. When we update, we hope to get performance improvements or bug fixes that apply to our use, but usually, you can't tell much by the update. Of course, one small change could have a big impact on performance or other aspects, so they're probably worth doing.
Can you skip an update? Some users prefer to decide which BIOS updates they want to use. They research and review what the BIOS change addresses, and if it doesn't apply to them, they hold off or wait until the next one, which should include all changes to date so they'd be fully caught up in a future update. If they can find documentation on what was changed, many users probably wouldn't be able to easily decide if an update is important or not, and just update them all. Some vendors just automate the updates for you and include it as part of a regular larger update.
There actually is a slight risk that a failed BIOS update could make a computer unbootable, such as if there was a power outage in the middle of the update and it corrupted the BIOS or left it incomplete. That's why it's probably best to never do a BIOS update during a storm or if there's risk of losing power, for example. Higher-end computers have fail-safes in place to protect against that, such as a dual BIOS that could restore a backup of the corrupted BIOS. Documentation on your motherboard would confirm whether you have that, and how you could recover from it should it need to be used.
For most people, updating the BIOS is done if it's relatively automatic or pushed out by the vendor. Waiting for a week or two (or more) for others to test it first isn't a bad idea.