iphone 15 pro restarts itself several times a day.

Hello!

There may be a hardware issue with the device. To rule that out, you can visit a Genius Bar or Apple Authorized Service Provider (AASP) and have them run diagnostics:

• Genius Bar Reservations: Genius Bar Reservation and Apple Support Options
• Locate Apple Stores & AASP’s: Find a Reseller 
• iPhone Service & Repair: iPhone Repair and Service - Apple Support

No idea when the next update will be, but iOS 18.6 Beta was just released, so you may see an update in the not too distant future.

Go to Settings>Battery>Battery Health. What does it say for Maximum Capacity? If it's 80% or less, you need a new battery. A failing battery would explain what you're seeing.

No software update will fix a hardware issue.

JRT2054 wrote:

Thanks. Maximum Capacity is 88%.

I have read a lot about people with issues with 18.5, so I was hoping it wasn't the phone.

You will always see reports that "the latest version of iOS ruined my phone." That doesn't mean there is really a problem. It's more often coincidence than causality.

If your phone is shutting itself down, you may still have a battery issue. Or some other hardware issue. Contact Apple. They can run many of the diagnostics remotely.

JRT2054 wrote:

I have read a lot about people with issues with 18.5, so I was hoping it wasn't the phone.

I have read a lot about people with issues for every version of iOS ever released. But what is “a lot”? For example, there are over an estimated 500 million iPhones with iOS 18.5. “A lot” is what? 1%? That would be 5 million. Have you read about 5 million? Of course you will see posts about problems, because only people with problems post about them. If you go into a hospital you will note that every patient in the hospital is sick or injured. Does that mean everyone in the world is sick or injured?

H1290 wrote:

…but iOS 18.6 Beta was just released…

Just to correct, it was iOS 18.6 Beta 2 that was released. Not the first Beta version of iOS 18.6.