Should I use this bandsaw?

There has been a bandsaw sitting in my step dad’s garage for a couple of months now and I wanted to see if it worked because it was a gift from one of his friends that bought a new one. Its at least 10 years old I think but its in okay condition. So when I powered it up the blade started moving and then the whole machine jerked slightly and then it went to full speed. This freaked me out and I immediately shut it off, thinking that it was broke or something. This happens every time I turn it on; it starts spinning, the whole machine jerks, then it reaches full speed and nothing else. It doesn’t make any other noises and it looks like its working fine. Is that normal for older ones, or is it a defect? I’ve used newer bandsaws in my school shop and my teacher always said if you hear an unusual noise coming from the machine turn it off and tell him. I tried cutting a piece of scrap pine on only about half an inch and it cut it fine the first time, the blade is old and dull so it needs replacing. However, the second time I was cutting it started to make strange noises while cutting. About every half second it would make a “duh duh” noise and would stop once I was done cutting. Is that normal? Its a 12” Sears saw so I know its nothing special and not very expensive but free is free. So should I use it, and is there anything that you guys can tell me that might be of some use? Any help will be appreciated, thanks.

-- Will Miller