Check the voltages at the corners of the RAM chips. If it is resetting as well as having video issues, that usually means the power supply needs to be rebuilt.
You need to test the voltages at the RAM chips to be sure about CPU board voltages. It is not uncommon for cracks at the headers or bad filter caps to drop the voltages dramatically in the RAM chips.
Measure the voltage at the 4 corners of one of the RAM chips.
The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground
The pins are numbered starting in the upper left corner (the side with the notch), going counter clockwise. If any of them are low or are fluctuating more than 0.1 V you need to check your power supply.
ken