[Update 2: in response to @telcoM's questions]

Make/model is Lenovo Thinkpad T540 (2014)

$ sudo lspci -s 4:0 -nnv
04:00.0 Network controller [0280]: Intel Corporation Wireless 7260 [8086:08b2] (rev 83)
    Subsystem: Intel Corporation Dual Band Wireless-AC 7260 [8086:c270]
    Flags: bus master, fast devsel, latency 0, IRQ 32
    Memory at f1400000 (64-bit, non-prefetchable) [size=8K]
    Capabilities: [c8] Power Management version 3
    Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [40] Express Endpoint, MSI 00
    Capabilities: [100] Advanced Error Reporting
    Capabilities: [140] Device Serial Number e8-2a-ea-ff-ff-15-8a-1f
    Capabilities: [14c] Latency Tolerance Reporting
    Capabilities: [154] Vendor Specific Information: ID=cafe Rev=1 Len=014 <?>
    Kernel driver in use: iwlwifi
    Kernel modules: iwlwifi

$ ethtool -i wlp4s0
driver: iwlwifi
version: 5.15.0-37-generic
firmware-version: 17.3216344376.0 7260-17.ucode
expansion-rom-version: 
bus-info: 0000:04:00.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no

$ sudo dmidecode -s system-product-name; sudo dmidecode -s system-sku-number; sudo dmidecode -s system-manufacturer
20BECTO1WW
LENOVO_MT_20BE
LENOVO

$ sudo dmidecode -s bios-version; sudo dmidecode -s bios-release-date
GMET91WW (2.39 )
06/03/2021

I have an IPhone(11) with Personal Hotspot turned on. Sometimes I would like to use my IPhone's Personal Hotspot as the internet connection for my laptop running Ubuntu 22.04 - when I'm in a place without wifi. If I try to ask my Ubuntu to connect to this Hotspot, sometimes the Hotspot ("Steve's IPhone") appears on the list of networks to which I can connect and connection is then possible, and sometimes it doesn't appear on the list. There is neither rhyme nor reason I can see as to when this connection will or won't be found. Turning wifi off and back on does not resolve the problem. Nor can the connection be seen with

sudo iwlist wlp4s0 scan | grep ESSID

(wlp4s0 being the interface my wifi is now using accord to ifconfig, though sometimes it shows up as wlan0, another mystery I'd like to understand someday.)

What is the explanation for this odd and inconsistent behavior? And does anyone know a way to force more consistent behavior in wifi connection using this system?

I have an IPhone(11) with Personal Hotspot turned on. Sometimes I would like to use my IPhone's Personal Hotspot as the internet connection for my laptop running Ubuntu 22.04 - when I'm in a place without wifi. If I try to ask my Ubuntu to connect to this Hotspot, sometimes the Hotspot ("Steve's IPhone") appears on the list of networks to which I can connect and connection is then possible, and sometimes it doesn't appear on the list. There is neither rhyme nor reason I can see as to when this connection will or won't be found. Turning wifi off and back on does not resolve the problem. Nor can the connection be seen with

sudo iwlist wlp4s0 scan | grep ESSID

(wlp4s0 being the interface my wifi is now using accord to ifconfig, though sometimes it shows up as wlan0, another mystery I'd like to understand someday.)

What is the explanation for this odd and inconsistent behavior? And does anyone know a way to force more consistent behavior in wifi connection using this system?

[update] a commenter below suggests that the above is too vague a description, but the vagueness is inherent in the problem. Sometimes it works, sometimes it doesn't, and I am unable to determine why it works or fails. The commenter suggest that it would be better to ask for information on how to troubleshoot this. That is a good idea, so I'll ask:

How might I troubleshoot this?