Good morning,
Sorry to hear about your mom. Regardless of how long ago she passed away, there's always a special place for her in your heart. I'm sure she would love it if you picked up her love of sewing.
I have the same Pfaff machine and I love it, so don't give up. :-). I would see if you can find a repair shop and have it checked out. Threading the bobbin and machine correctly are really important so you want to make sure that's being done correctly.
Sometimes there are pieces of thread that get caught underneath that can cause problems. Make sure there aren't any extra threads in the bobbin area.
I've not had any problems with losing the threads when I start sewing. In fact, that's one thing I like about the machine. It seems to start without a lot of fuss.
It may just need a good cleaning or a few adjustments. Hope you're able to get it worked out.
Happy New Year.