Turn key and nothing

[RROSIN1]

I started my car this morning with no problem(83' 300D). Drove to my sons daycare to drop him off and shut the car off while i was inside. When i went to start the car i turned the key to warm the glow plugs. Glow plug light came on for about two seconds and went off. i turned the key and nothing. With key in glow plug on position the tachometer bounces all over andthe other gauges do the same. Door open buzzer and dome lights come on but are faint. Seat-belt light in dash is faint also.It is like there is a weak battery and no starter. This is my only transportation. Please HELP.