Firefox hangs for 2 0r 3 seconds about every 10 seconds. This problem does not occur when using IE browser.
This may be due to a problem with an add-on. Follow the procedure in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to see if it helps.
Your above posted system details show outdated plugin(s) with known security and stability risks.
Update the Java plugin to the latest version.
I also had this problem but managed to resolve it by disabling the antiphishing toolbar that Bitdefender had installed in Firefox.