Desire keeps rebooting

Hi,
I have a HTC Desire s/n HT09 model A8183
i got the phone thru Telstra in Australia approx 15mths ago ...
started having the reboot problem around 6mths ago ...

Also, have never been able to do an upgrade when the phone prompts me to ... the upgrade notification just keeps going & going with no end ... i cancelled after about 10 hrs - thought that it shouldnt really take that long ? .. have tried a couple times the same thing happens !

From memory the rebooting started after i downloaded a game from the market ... after a while i uninstalled the game but the constant rebooting never ceased 
My phone used to just reboot when i went into google or social media .. but now reboots even when i am trying to send a SMS message or even just on a normal phone call - Even when the phone is sitting idle it just switches off & can sometimes go into a kind of like spasm .. where it will just go to start up then switch off then start up then switch off ... over & over & over ... untill i am forced to remove the battery ! ... the battery also is very HOT !

I really thought it was just my phone .. i got a DUD .. but after looking online & doing some research .. it looks like i am not alone .. & worse still it has been happening for some time .. well before i purchased my phone.

After reading these posts i thought about doing a factory reset . .but then i see that doesnt work either .. so is that a waste of time ? ... should i do it ? ... worried about losing all my contact etc .. what does a factory reset do ?

It looks like nothing can be done apart from sending it back & if your lucky enough you get a new phone sent to you .. i don't really want to wait weeks & weeks for it to be returned probably not fixed .. don't have a spare phone 
Just so annoyed & frustrated .. HTC should do a recall of these phones & send everyone back an upgraded New phone back .. we paid for a phone that basically does not do what it is intended to .. i bragged to everyone when i got this phone saying how good it was - i LOVED it .. but now can't wait for the contract to finish so i can get another phone .. i can't recommend this phone to anyone if HTC aren't willing to fix the problem they so clearly know about & are doing nothing to rectify. ...

Righto ... feel better now ... have had my rant .. 

any suggestion would be appreciated

 thx for the reply ...

i used to have my phone in a protective case - hard plastic .. but took it off when i noticed the overheating happening .. plus with the constant need to remove the battery the case was in the way & being hard plastic was tricky to get off & on.

Had a look in the market to try your suggestion .. but my phone rebooted .. will keep trying & hope that i actually get the phone explorer installed.

cheers

just got my Desire back from vodafone, new mainboard, i already tested in sunny Lisbon (27c) working in the sun, for navigation in the car with google maps navigation,  
the old one, in direct sun lite it would not stay on for 5m.
Now it is ok!
and since it is a new mainboard and IMEI, i have a renew 2 YEAR WARRANTY . thx voda... lol

but that's not all, they also changed my screen from a SLCD to a OMOLED
and i don't think that's ok!

when i delivered my desire to vodafone, they lent one other htc desire to me, it also was amoled, but it add much better viewing angle, and less tending to blue.

my new screen was a very poor viewing angle because the colors tend to much to the blue when i tilt the phone, it also is very bright, does not have as much definition as the SLCD, and i think the one voda lent to me ad also better definition,  but at least the black is really black and color very vivid!

do you think that what i have  seen, 3 different screen's in 1 week, and considering the characteristics of my new screen, are normal for amoled screen? ?

thx in advance (sorry for the inglish)

Yes me too! Pity!