Hi Gsterken,
To get the valid acceleration from the ADXL362, you need to enable it firstly by writing 0x02 to register 0x2D (POWER_CTL).
I would suggest you to read DEVID_AD, DEVID_MST, PARTID firstly to make sure there is no problem with your reading program. Then write any value to any R/W register, like POWER_CTL, read back to make sure there is also no problem with writing program.
After these, you can use all the default configration, just enable ADXL362 by writing 0x02 to register 0x2D. Then read 0x0E - 0x13 for three axis output. If you put board flatly on the table, the output should be around 0g, 0g, 1g for X, Y, Z. Change to LSB, it should around 0, 0, 1000LSB.
Refer to temperature output, it could be any value in room temperature since the temperature sensor built in ADXL362 is not trimmed for test the absolute temp, it is used to test the temperature change to calibrate the acceleration. Eg: in 25C room temperature, the ADXL362 output could be 0C. But when the temperature increase to 26C, the ADXL362 output will be 1C. It can reflect the temperature change correclty.
Hope these can help.
BR
Neil