I saw an article recently about the new 5G cell bands using more power for transmit and receive. If this is a very new phone with 5G enabled there might be something like going on. There is probably a setting on the phone to turn 5G on/off if it is using it.

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1985 300D
The rest:
1957 MGA (comatose)
1965 Falcon (sleeping)
1966 E-100 (rust test in progress)
1976 Ford 3400 D Tractor (workhorse)
1978 Mercury Zephyer (5L playtoy)
1995 Isuzu NPR D (fetcher)
1998 Subaru Legacy (Spare)
2000 Toyota Sienna (School bus)
2008 Toyota Prius (Commuter)