2004 sebring, keeps overheating especially on hot days. boiling in reservior and spewing coolant on inner hood. fixed things and last for a couple of days and starts again.

You likely overheated the engine/transmission to the point of a coolant boil over. 10 minutes of struggling like that can cause a lot of problems. I burned a belt off of my work truck because of all of the strain I put on the motor when I was in a similar situation. Replace the lost coolant if it registers in the overflow tank, make sure you still have all of your belts and keep an eye on the temperature gauge for a couple of days and keep an eye out for any more coolant under the vehicle. Likely the damage is localized to just a loss of coolant from boiling over. However, I'd suggest in the future that if you are stuck like that again, give the transmission a chance to cool down. You may want to consider having the transmission fluid serviced if it smells burnt at all, you may have used up some of the service life of the fluid by overheating it ( and heat kills transmissions! )

You say its overheating but not loosing coolant, is it truly overheating or is the gauge telling fibs. You seem to have done all the right things but if it retains its coolant I don't see a reason other than the gauge. When you next run it and it shows overheat on the gauge, get a rag and very gently crack the rad cap. If hot water comes out but no steam then it may not be too hot. If after a few minutes you are able to safely remove the cap see what the gauge says with the key on but not running. If the gauge says its still high then the gauge is faulty because its obviously not boiling the coolant.
Lastly, have the rad cap checked or replaced because the cap is crucial to the boiling point of the coolant. Make sure the cap pressure setting is right for your vehicle, too low and it will boil easier.

You could have a pin hole in your hose or in your radiator.

you have a blown head gasket.. doesn't have to have coolant in the oil for a blown head gasket... if hoses are rock hard when running then you have exhaust leaking into the coolant via a blown head gasket...

You have an air bubble at the top of the engine.
The antifreeze spewing out of the overflow happens due to your perfectly functional radiator cap
passing the overheated coolant/air mixture out of the system into the reservior (in an attempt
to relieve overpressurization of the cooling system)
The sudden nature of your overheating comes from the boiling of the inadequate amount of
coolant/antifreeze in your engine, since it cant properly cool the engine, so it boils (overheats quickly), and pressure rises immediately within the cooling system.
The Fix is free: locate and open the (air) bleeder port at the top of the engine, and add the usual
50% coolant/50% water mixture to the radiator until the radiator is full to the level indicated in
your owner's manual (or the "Full" line). Then close the bleeder port and replace the rad (radiator)
cap.
The air bleeder port is normally located near the thermostat, and should be opened each time
that coolant is added to the radiator. The air bleeder port need not be opened when adding
50/50 coolant to the reservior, since the rad cap is going to be closed while adding coolant
to this part of the cooling system.
Warning: driving beyond the point where your engine temperature gauge indicates overheating will
destroy the car's engine - it'll seize up due to overheating, and the only fix for a seized/burned-up
engine is replacement (of the engine). Seizing an engine is really easy with an air bubble in the
top of the engine - you could easily burn up/warp the head, necessitating replacement of the head
and head gasket.

You have air in the top of the engine.
The antifreeze spewing out of the overflow happens due to your perfectly functional radiator cap
passing the overheated coolant/air mixture out of the system into the reservior (in an attempt
to relieve overpressurization of the cooling system)
The sudden nature of your overheating comes from the boiling of the inadequate amount of
coolant/antifreeze in your engine, since it cant properly cool the engine, except for the first
10-25 minutes of operation - after that, it boils (overheats quickly), then pressure rises immediately
within the cooling system.
The Fix is free: locate and open the (air) bleeder port at the top of the engine, and add the usual
50% coolant/50% water mixture to the radiator until the radiator is full to the level indicated in
your owner's manual (or the "Full" line). Then close the bleeder port and replace the rad (radiator)
cap.
The air bleeder port is normally located near the thermostat, and should be opened each time
that coolant is added to the radiator. The air bleeder port need not be opened when adding
50/50 coolant to the reservior, since the rad cap is going to be closed while adding coolant
to this part of the cooling system.
Warning: driving beyond the point where your engine temperature gauge indicates overheating will
destroy the car's engine - it'll seize up due to overheating, and the only fix for a seized/burned-up
engine is replacement (of the engine). Seizing an engine is really easy with an air bubble in the
top of the engine - you could easily burn up/warp the head, necessitating replacement of the head
and head gasket.

thermostat

I would expect this is more to do with a low coolant level than an electrical issue. If your coolant is low when you turn off the headlights your engine revs will increase slightly increasing the pressure in your coolant system and pushing fluid into your heater core.
Check your coolant reservior when your car is cold (first thing in the morning), it should be at max cold. If it is lower than this you may not have warm coolant in your heater core.
If this is the case...then where did your coolant go?
Most likely the thermostat/temp housing is leaking...replaced both on my two 2001 sebrings...common issue..~$150 for parts and a little awkward to install but fairly easy fix.

The easiest way is to usually just remove the lower radiator hose. All of the coolant will come out in a couple of minutes so you will need to have a big bucket. Around 3-4 gallons will come out. It sounds like the shop used too much water in the coolant mix. It is supposed to be 50/50 or better(better being more than 50% straight coolant) and water. If you drain what they put in there and refill with straight coolant ( not the premix from the store but rather the non-mixed stuff) you probably wont even have to go back to the mechanic.
Your coolant sounds like it is boiling which can be very bad for the engine. Once you remove the lower radiator hose, just reconnect it and fill it back up. It will be the largest hose going into the radiator at the bottom of the radiator. There may be a bleed screw on the top of the thermostat housing. If so open it with the car running till coolant bleeds out in a steady stream then close it and your done.

I hope this helps!! Thanks!!!

the engine is overheating or u have a defective radiator cap