'Basically it takes about 2-5 revolution to get it back going again. "
I would guess that you are in the wrong gear and or not pedaling fast enough. You have to spin the rear cassette faster than the rear wheel is spinning to engage it.
Chain tension can be chanaged by adjusting the derailer, or changing the length.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.