Always have to "Start" and "restart" to start! HELP!

OK, I am a complete non-understanding PC user, but recently have had this problem and its starting to wrankle BIG STYLE!
Whenever we start our PC, it either stops responding, doesn't load correctly in appearance (task bar goes white/grey rather than blue) and then needs rebooting... or crashes out of IE on first starting it by rebooting itself!
Either way, we start up, then PC needs rebooting and then all is hunky dory. Thats it, without fail, always the same, never up and running first time!:cry
To my knowledge, there was no new software installed by me or mine.
Any ideas?:confused

(ps, I used this wonderful site to install AVG free, Ad-Aware and Spybot S&D ages ago, and update frequently. These have highlighted nothing.)