Hey! We’ll fix your Nest stuck on a boot loop (restarting, stuck on the G logo, or never finishing setup). I’ll ask a few quick questions so we pick the right recovery path and don’t accidentally wipe settings you need:
• Which device: Nest Learning Thermostat (round with click ring), Nest Thermostat E, or the newer Nest Thermostat (2020) (touch bar)?
• What do you see during the loop: Google “G”, blank screen, blinking red, blinking green, or “Restarting…”?
• Did anything change right before it started: power outage, HVAC work, new Wi-Fi/router, or a software/firmware update?
• Is it wall-mounted on HVAC wires (Rc/Rh/W/Y/G) or on a stand/USB power? Any C-wire connected?
Once I know that, we can fix the Nest reboot loop step-by-step (power, battery, wiring, then reset only if needed).

Got it — after a power flicker, a Nest thermostat boot loop is most often one of these:
• Low battery (the thermostat can’t hold enough charge to finish startup, so it keeps restarting).
• Unstable power from the HVAC (loose wire at Rc/Rh/C, aging transformer, or a short that makes voltage dip).
• A stuck restart after a crash (fixable with a clean restart), and only rarely a firmware corruption that needs a reset.

The safe order is: charge → confirm steady power → restart → check wiring. We’ll try “no data loss” steps first, then factory reset only if the Nest keeps cycling.

Perfect — no C-wire + power event = we start with battery/charging, because that’s the fastest fix for a Nest stuck on the G logo.
Step 1 — Pull the Nest off the wall and charge it (quick boot-loop fix)
1) Gently pull the thermostat display straight off the base (the wires stay on the base).
2) Plug the display into USB power (a phone charger is fine). Let it charge for at least 30–60 minutes (longer is okay).
3) While charging, press the ring once — if you see a battery icon or it stays stable longer, that’s a strong sign this is a low battery reboot loop.

Step 2 — Do a clean restart (no factory reset yet)
After it has some charge, hold the thermostat ring down for about 10 seconds until the screen goes dark, then release. This forces a clean reboot that can break a stuck restarting cycle.

If it boots normally on USB but boot-loops again after putting it back, that points to HVAC power / wiring / C-wire stability.

That’s a super useful clue. If the Nest is stable on USB but keeps restarting on wall power, the base is not delivering consistent power.
Step 3 — Quick wall-power checks (common boot loop causes)
1) Turn off power to HVAC at the breaker (safety first).
2) Remove the Nest display and inspect the wires in the base: make sure each conductor is fully inserted and the tab is locked down. A slightly loose Rc/Rh connection can cause voltage dips and a Nest reboot loop.
3) Look for stray copper strands touching neighboring terminals (a tiny short can cause repeated restarts).
4) Confirm your wiring label set matches the base (for many systems you’ll see R (Rc/Rh), W (heat), maybe Y (cool) and G (fan)).

Step 4 — If there’s no C-wire, reduce power stress
Nest models can “power steal” through control wires, but some furnaces/air handlers don’t like it. That can show up as random restarts or stuck on startup after a flicker. Long-term fix is often adding a C-wire or a compatible power accessory — but first we’ll confirm it’s actually power instability (not a corrupted setting).

It can be, but we can separate “power” from “software” in a clean way.
Step 5 — Isolate the root cause (power vs firmware/settings)
• If it’s stable on USB for hours but reboots on the wall within minutes/hours, that’s still power delivery (wiring, transformer, or lack of C-wire).
• If it reboots even while on USB after you did a clean restart, then we consider a corrupted config and move toward reset options.

Quick test: charge it again for 30 minutes, then put it back on the wall and don’t touch Wi-Fi for 10–15 minutes. If it stays stable until you open Wi-Fi / app pairing, it may be crashing during network setup (rare, but it happens).

Also: a flashing red or frequent blank screen usually screams battery/power. A stable screen that reboots only at certain menus can hint at settings/firmware.

Yes — and we’ll do it in the least destructive way first.
Step 6 — “Safe” recovery options (in order)
1) Restart (no data loss): press and hold the ring ~10 seconds until it reboots.
2) If you can reach Settings: go to Settings → Reset → Restart (cleaner than a forced reboot).
3) Only if it still boot-loops: Settings → Reset → Factory Reset (this wipes schedules, Wi-Fi, and app pairing).

Because your pattern screams power instability, a factory reset might “appear” to help for a short time (fresh setup uses less), but the loop can return unless we stabilize power (often by adding a C-wire or fixing the loose/weak connection).

If you need heat immediately: once it boots, set a basic heat target locally on the Nest and avoid re-pairing for a bit. Then we can finish the stable setup (Google Home/Nest app) after power is solid.

Totally fair — and you have options even if you can’t pull a new cable.
Step 7 — Permanent fixes for Nest reboot loop (power stability)
• Add a C-wire (best): many homes already have an unused conductor in the thermostat bundle — it’s just not connected at the furnace/air handler. If there’s an extra wire behind the Nest base, we can often repurpose it as C without running anything new.
• If there’s no spare conductor: a compatible power accessory (depending on your system) can provide steady power so the Nest doesn’t “power steal” and crash into a boot loop during calls for heat/cool.
• Transformer/voltage dips: if your HVAC transformer is weak, or there’s a short/intermittent connection, voltage can sag when the furnace starts — exactly when you’ll see Nest keeps restarting. That’s when checking connections at the control board (or having an HVAC tech verify 24V stability) matters.

If you tell me the wires you have (R, W, Y, G, O/B, etc.) and whether it’s furnace + AC or heat pump, I can point to the most likely “no-new-wire” solution.

Yes — a blinking green on many Nest thermostats often indicates it’s restarting / installing / trying to connect, and if power is unstable it can get stuck in that state and look like an endless reboot loop.
Step 8 — Pairing + Wi-Fi steps (after power is stable)
• Don’t fight the app pairing while it’s rebooting — stabilize first (charge + wall power check).
• Once it boots and stays on for 10–15 minutes: open Google Home (or Nest app if your model uses it), add the thermostat, and complete Wi-Fi setup.
• If it won’t stay online long enough to pair: that’s another sign the device isn’t getting steady power from the base (again, C-wire/transformer/wiring).

If you *do* end up factory-resetting, it will show up as “new device” and you’ll need the pairing code — totally normal after a Nest factory reset.

Love it — that matches the pattern perfectly.
Summary: For a Nest stuck on a boot loop or stuck on the G logo, the fastest win is to charge via USB, then do a clean restart. If it’s stable on USB but restarts on the wall, focus on HVAC power: reseat wiring, eliminate shorts, and consider a C-wire (or another steady-power solution) so the thermostat battery doesn’t drain and crash again. If you’re unsure which wire can be used as C or whether your system supports a power accessory, open the chat — we’ll map it safely step by step.