My Toyota Previa is going good then all of a sudden it will start missing and lose power for a couple seconds then go good. It is getting worse happening more often missing and shuddering

SOURCE: Transmission shifts into 5th gear and loses power

start checking the trans fluid level, a trans filter change and trans flush should help.

SOURCE: engine loses power for a second then regains full power

if you have eng light on scan it OBD 2 tester find code error don"t gue$$ however that ign coil would be in my best interest! I would get it tested if your not able to do so your self!

SOURCE: missing all of a sudden on highway

Mass Air Flow Sensor, Coil Packs, Ignition Wires, Spark plugs. check all of those. MAF (Mass Air Flow Sensor) it would want to quit in park and sometimes the check engine light would come on also it would skip a little when you got on it around 3,000 rpm or so.

SOURCE: After several minutes of driving, the engine starts shuddering and losing power like it is going to die

Sounds like your clutch is glazed, warped and/or going out.

SOURCE: 1991 Toyota Previa won't start

low voltage to starter. Check battery for proper charge (must be 12.5+ volts), clean and tighten battery terminals. If below 12.5 volts, charging or battery replacement is needed. Hopefully this helpd