Computer lags and looses internet connection daily

Macrium free is a good imaging/backup software many here use without any issues. For data files, sync software like FreeFileSync works very good.

I ran a malware scan with Malwarebytes and removed any and all suspicious items (I think 37 in total), but my computer still lags after startup.

It isn't really that bad restarting my computer everyday, but it can be irritating when I'm in the middle of something and it stops working. I am more upset that the problem is there, though, even if it only takes a minute or two to "resolve." I just want the problem to be fixed.
Do you know of any good anti-virus software? I almost always use Opera if that helps anything.
I've only had a windows computer for about a year now, so I'm still a "greenie" to threat prevention and such.

I have Microsoft Security Essentials, but that's it I think.
Also, I ran the Eset scanner and it removed one item, but my computer still lags after startup.

Is it possible that this is being caused by a bad driver or something. I was talking to my friend (who built the computer, and from whom I bought it from) a bit ago, and he said that the wifi card had shotty internet connectivity and that it caused the computer to act up. I don't know how accurate that sounds; my brother (who's quite computer savvy) said that the wifi card wouldn't be the issue for a slow computer. And since I've had the card, it connects to the internet very well for me (other than during the lag sessions), and did so for a few months after I bought it from him.

It can cause issues if it is somehow damaged, is it an add-on wifi card? Can you remove it?

Yes, it can be removed. I doubt it's damaged. If so, not too severely, because it's only ever been in two computers and it's only ~2-3 years old.