Negative Voltage Shift from Blocking Cap for Amplifier
You could have potentially up to 3uA of bias current.  For simplicity, we'll assume 1uA.

The negative input, with its 1k to ground, will see a 1mV offset inspired by the bias current.  The positive input, with 100K to ground, will see 100mV, for a difference of 99mV.

With your gain of 500, that 99mV offset on the input becomes 49.5V on the output.

Try replacing R1 with a 1K and it should be better.  This will give you a high-pass corner of about 160Hz unless you increase C1.