What it means

Garmin's 'The camera is too hot' message (it then shuts down to protect itself) means the internal temperature has climbed past the safe limit for the battery and image sensor.
Nine times out of ten it's a parking problem — a small black camera stuck to the inside of a windscreen in direct sun heats up fast.
It powers back on by itself once it cools down.

Affected Models

Garmin Dash Cam Mini 2 (small body, heats quickly)
Garmin Dash Cam 47 / 57 / 67W
Garmin Dash Cam Tandem
Garmin Dash Cam Live (parking mode on hot days)

Common Causes

Parked in direct sun with the camera on the windscreen
Parking Mode left recording on a hot day with the car closed up
Mounted low behind heavily tinted or heated glass with no airflow
Internal lithium battery failing and generating heat — the giveaway is overheating even on a cool day or with the AC running

How to Fix It

Let it cool down.

Move the car into shade, or take the camera off its mount and bring it indoors.
Fifteen to thirty minutes is usually enough.
It'll power back up on its own once the temperature drops — there's no reset to do.
Move the mount up high.

Mount the camera near the rear-view mirror.
Many windscreens have a shaded band along the top, and that spot also catches airflow from the dash vents.
Low on the glass in full sun is the hottest place you can put it.
Rethink Parking Mode on hot days.

Continuous recording while parked in 40°C-plus heat will trip this again and again.
Some Garmin models let you set a temperature cutoff for parking mode — turn that on.
Or accept that parking mode isn't practical on the hottest days.
Shade the windscreen.

A reflective sunshade across the inside of the glass, or simply parking nose-out so the windscreen faces away from the sun, makes a big difference to how hot it gets behind the screen.
Watch for overheating in cool conditions.

If you've done all the above and it still overheats when it's not hot out, that's the battery — see the note above about contacting Garmin.
Don't keep using a dash cam that runs hot for no external reason.

When to Call a Professional

If the camera overheats in normal conditions — a mild day, AC on, not in direct sun — the internal battery is likely failing and may be starting to swell.
Stop using it.
A swelling lithium cell in a hot car is a genuine fire risk.
Contact Garmin support about repair or replacement rather than carrying on with it.