Old fluorescent fixtures has a starter rather than a ballast, and you need to hold the switch down to charge it to light.
I don't think it is a switch fault at all ... If it is, after you have the switch on by holding it, it would still be on (just as if you have used a jumper) when the timer cuts power and be on when the power turns on ....
So your best bet is a new ballast.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.